Objects Of Various Shapes Research Articles

The effects of short-term and long-term learning on the responses of lateral intraparietal neurons to visually presented objects.

The lateral intraparietal area (LIP) is thought to play an important role in the guidance of where to look and pay attention. LIP can also respond selectively to differently shaped objects. We sought to understand to what extent short-term and long-term experience with visual orienting determines the responses of LIP to objects of different shapes. We taught monkeys to arbitrarily associate centrally presented objects of various shapes with orienting either toward or away from a preferred spatial location of a neuron. The training could last for less than a single day or for several months. We found that neural responses to objects are affected by such experience, but that the length of the learning period determines how this neural plasticity manifests. Short-term learning affects neural responses to objects, but these effects are only seen relatively late after visual onset; at this time, the responses to newly learned objects resemble those of familiar objects that share their meaning or arbitrary association. Long-term learning affects the earliest bottom-up responses to visual objects. These responses tend to be greater for objects that have been associated with looking toward, rather than away from, LIP neurons' preferred spatial locations. Responses to objects can nonetheless be distinct, although they have been similarly acted on in the past and will lead to the same orienting behavior in the future. Our results therefore indicate that a complete experience-driven override of LIP object responses may be difficult or impossible. We relate these results to behavioral work on visual attention.

Exo-Glove: A Wearable Robot for the Hand with a Soft Tendon Routing System

Soft wearable robots are good alternatives to rigid-frame exoskeletons because they are compact and lightweight. This article describes a soft wearable hand robot called the Exo-Glove that uses a soft tendon routing system and an underactuation adaptive mechanism. The proposed system can be used to develop other types of soft wearable robots. The glove part of the system is compact and weighs 194 g. The results conducted using a healthy subject showed sufficient performance for the execution of daily life activities, namely a pinch force of 20 N, a wrap grasp force of 40 N, and a maximum grasped object size of 76 mm. The use of an underactuation mechanism enabled the grasping of objects of various shapes without active control. A subject suffering from paralysis of the hands due to a spinal cord injury was able to use the glove to grasp objects of various shapes.

2P1-W08 Granular Jammingに基づく組立作業用ユニバーサルハンド

This paper proposes a novel robotic hand that can grasp objects of various shapes used for assembly tasks. The proposed hand uses granular jamming combined with a multiple finger mechanism. Due to the effect of granular jamming, the pose of a grasped object does not change during an assembly operation. The proposed hand has four fingers where two are active ones and the other two are passive ones. We use the passive fingers to orient an object placed on a table before the active fingers are closed to grasp it. The active fingers can adapt to the shape of an object due to its underactuated mechanism. Experimental results on assembly of two kind of parts are shown to validate the effectiveness of our proposed hand.

Technique for calculating the effective scattering area of diffusely reflecting objects of complex shape

This paper presents a technique for calculating the effective scattering area (ESA) of objects of various shapes and with various reflective characteristics of coatings for various angles of incidence of the illuminating laser radiation. The technique is based on representing the surface of a body of complex shape as separate elements with a simple surface shape with specified diffuse-reflectance functions. The ESA from each segment with a simple surface shape is calculated, and then all the ESAs are summed. Formulas are given for calculating the ESA from the individual segments of objects with a simple surface shape.

Monte Carlo simulation of light transport in turbid medium with embedded object--spherical, cylindrical, ellipsoidal, or cuboidal objects embedded within multilayered tissues.

Monte Carlo modeling of light transport in multilayered tissue (MCML) is modified to incorporate objects of various shapes (sphere, ellipsoid, cylinder, or cuboid) with a refractive-index mismatched boundary. These geometries would be useful for modeling lymph nodes, tumors, blood vessels, capillaries, bones, the head, and other body parts. Mesh-based Monte Carlo (MMC) has also been used to compare the results from the MCML with embedded objects (MCML-EO). Our simulation assumes a realistic tissue model and can also handle the transmission/reflection at the object-tissue boundary due to the mismatch of the refractive index. Simulation of MCML-EO takes a few seconds, whereas MMC takes nearly an hour for the same geometry and optical properties. Contour plots of fluence distribution from MCML-EO and MMC correlate well. This study assists one to decide on the tool to use for modeling light propagation in biological tissue with objects of regular shapes embedded in it. For irregular inhomogeneity in the model (tissue), MMC has to be used. If the embedded objects (inhomogeneity) are of regular geometry (shapes), then MCML-EO is a better option, as simulations like Raman scattering, fluorescent imaging, and optical coherence tomography are currently possible only with MCML.

Exploring teleimpedance and tactile feedback for intuitive control of the Pisa/IIT SoftHand.

This paper proposes a teleimpedance controller with tactile feedback for more intuitive control of the Pisa/IIT SoftHand. With the aim to realize a robust, efficient and low-cost hand prosthesis design, the SoftHand is developed based on the motor control principle of synergies, through which the immense complexity of the hand is simplified into distinct motor patterns. Due to the built-in flexibility of the hand joints, as the SoftHand grasps, it follows a synergistic path while allowing grasping of objects of various shapes using only a single motor. The DC motor of the hand incorporates a novel teleimpedance control in which the user's postural and stiffness synergy references are tracked in real-time. In addition, for intuitive control of the hand, two tactile interfaces are developed. The first interface (mechanotactile) exploits a disturbance observer which estimates the interaction forces in contact with the grasped object. Estimated interaction forces are then converted and applied to the upper arm of the user via a custom made pressure cuff. The second interface employs vibrotactile feedback based on surface irregularities and acceleration signals and is used to provide the user with information about the surface properties of the object as well as detection of object slippage while grasping. Grasp robustness and intuitiveness of hand control were evaluated in two sets of experiments. Results suggest that incorporating the aforementioned haptic feedback strategies, together with user-driven compliance of the hand, facilitate execution of safe and stable grasps, while suggesting that a low-cost, robust hand employing hardware-based synergies might be a good alternative to traditional myoelectric prostheses.

Neurocognitive robot-assisted therapy of hand function.

Neurocognitive therapy, according to the Perfetti method, proposes exercises that challenge motor, sensory as well as cognitive functions of neurologically impaired patients. At the level of the hand, neurocognitive exercises typically involve haptic exploration and interaction with objects of various shapes and mechanical properties. Haptic devices are thus an ideal support to provide neurocognitive exercises under well-controlled and reproducible conditions, and to objectively assess patient performance. Here we present three neurocognitive robot-assisted exercises which were implemented on the ReHapticKnob, a high-fidelity two-degrees-of-freedom hand rehabilitation robot. The exercises were evaluated for feasibility and acceptance in a pilot study on five patients suffering from different neurological disorders. Results showed that all patients were able to take part in the neurocognitive robot-assisted therapy, and that the proposed therapy was well accepted by patients, as assessed through subjective questionnaires. Force/torque and position measurements provided insights on the motor strategy employed by the patients during the exploration of virtual object properties, and served as objective assessment of task performance. The fusion of the neurocognitive therapy concept with robot-assisted rehabilitation enriches therapeutic approaches through the focus on haptics, and could provide novel insights on sensorimotor impairment and recovery.

Numerical simulation of water impact of solid bodies with vertical and oblique entries

The flow problem of hydrodynamic impact during water entry of solid objects of various shapes and configurations is simulated by a two-fluid free surface code based on the solution of the Navier–Stokes equations (NSE) on a fixed Cartesian grid. In the numerical model the free surface is captured by the level set function, and the partial cell method combined with a local relative velocity approach is applied to the simulation of moving bodies. The code is firstly validated using experimental data and other numerical results in terms of the impact forces and surface pressure distributions for the vertical entry of a semi-circular cylinder and a symmetric wedge. Then configurations of oblique water entry of a wedge are simulated and the predicted free surface profiles during impact are compared with experimental results showing a good agreement. Finally, a series of tests involving vertical and oblique water entry of wedges with different heel angles are simulated and the results compared with published numerical results. It is found that the surface pressure distributions and forces predicted by the present model generally agree very well with other numerical results based on the potential flow theory. However, as the current model is based on the solution of the NSE, it is more robust and can therefore predict, for example, the formation and separation of the thin flow jets (spray) from surface of the wedge and associated ventilation phenomena for the cases of oblique water entry when the horizontal velocity is dominant. It is also noted that the potential flow theory can result in over-estimated negative pressures at the tip of the wedge due to its inherent restriction to nonseparated flows.

Percepcja rozmiaru i wielkości rezonujących obiektów

BackgroundWe investigated the ability of naïve, untrained listeners to identify the physical parameters of 3D polystyrene objects from listening to single impulse sounds generated by an impact collision. We were specifically interested in the perception of object shape and object size and their interaction.Material and MethodsTwenty polystyrene objects of various shapes (spheres, hearts, cubes, eggs, rings, and cones) and sizes (between 64 cm3 and 2278 cm3 ) were used in three experiments investigating size and shape perception. In the first experiment, the task was to identify the ‘odd one out’ of three sounds originating from objects of different shape or size. In the second experiment the task was to identify the shape and size of an object just by listening to it. In the third experiment the task was to rate how similar two sounds were.ResultsResults show that listeners were able, to a degree, to identify the size and shape of objects without reference and in relation to each other. Multidimensional scaling suggests that shape (most salient) and size (second most salient) are the predominant perceptual dimensions.ConclusionsWe conclude that humans, to some degree and without training and without prior experience, have the ability to infer the physical properties of object size and shape by listening to single impulse sounds. Size and shape seem to be independent and are the most salient parameters.

ANALYSIS OF SCATTERING FROM THREE-DIMENSIONAL OBJECTS BURIED BELOW A RANDOM ROUGH SURFACE BY MONTE-CARLO MPSTD METHOD

This paper presents a Monte-Carlo multidomain pseu- dospectral time-domain (MPSTD) algorithm developed for the analy- sis of scattering from a three dimensional (3D) object buried below a random rough surface separating two half spaces. In the development, special attention is paid to the 3D computation domain decomposition and subdomain mapping involving the random rough surface as well as the subdomain patching along the rough surface. The Mote-Carlo MPSTD algorithm is then employed to determine the scattering of 3D objects of various shapes and electromagnetic properties; embedded in the lower half space with difierent permittivity and the roughness of the random rough surface may vary. Sample numerical results are presented, validated, and analyzed. Through the analysis, it is ob- served that the roughness of the random rough surface and the elec- tromagnetic properties of the lower half space can signiflcantly afiect the scattered signature of the buried object.

Experimental evaluation of ballistic hazards in imaging diagnostic center.

SummaryBackground:Serious hazards for human health and life and devices in close proximity to the magnetic resonance scanners (MRI scanners) include the effects of being hit by ferromagnetic objects attracted by static magnetic field (SMF) produced by scanner magnet – the so-called ballistic hazards classified among indirect electromagnetic hazards. International safety guidelines and technical literature specify different SMF threshold values regarding ballistic hazards – e.g. 3 mT (directive 2004/40/EC, EN 60601-2-33), and 30 mT (BMAS 2009, directive proposal 2011). Investigations presented in this article were performed in order to experimentally verify SMF threshold for ballistic hazards near MRI scanners used in Poland.Material/Methods:Investigations were performed with the use of a laboratory source of SMF (0–30 mT) and MRI scanners of various types. The levels of SMF in which metal objects of various shapes and 0.4–500 g mass are moved by the field influence were investigated. The distance from the MRI scanners (0.2–3T) where hazards may occur were also investigated.Results:Objects investigated under laboratory conditions were moved by SMF of 2.2–15 mT magnetic flux density when they were freely suspended, but were moved by the SMF of 5.6–22 mT when they were placed on a smooth surface. Investigated objects were moved in fields of 3.5–40 mT by MRI scanners. Distances from scanner magnet cover, where ballistic hazards might occur are: up to 0.5 m for 0.2–0.3T scanners; up to 1.3 m for 0.5T scanners; up to 2.0 m for 1.5T scanners and up to 2.5 m for 3T scanners (at the front and back of the magnet).Conclusions:It was shown that SMF of 3 mT magnetic flux density should be taken as the threshold for ballistic hazards. Such level is compatible with SMF limit value regarding occupational safety and health-protected areas/zones, where according to the Polish labor law the procedures of work environment inspection and prevention measures regarding indirect electromagnetic hazards should be applied. Presented results do not support the increase up to 30 mT of the SMF limit for protected area.

Relaxation properties in a diffusive model of extended objects on a triangular lattice

In a preceding paper, Šćepanović et al. [J.R. Šćepanović, I. Lončarević, Lj. Budinski-Petković, Z.M. Jakšić, S.B. Vrhovac, Phys. Rev. E 84 (2011) 031109. http://dx.doi.org/10.1103/PhysRevE.84.031109] studied the diffusive motion of k-mers on the planar triangular lattice. Among other features of this system, we observed that the suppression of rotational motion results in a subdiffusive dynamics on intermediate length and time scales. We also confirmed that systems of this kind generally exhibit heterogeneous dynamics. Here we extend this analysis to objects of various shapes that can be made by self-avoiding random walks on a triangular lattice. We start by studying the percolation properties of random sequential adsorption of extended objects on a triangular lattice. We find that for various objects of the same length, the threshold ρp∗ of more compact shapes exceeds the ρp∗ of elongated ones. At the lower densities of ρp∗, the long-time decay of the self-intermediate scattering function (SISF) is characterized by the Kohlrausch–Williams–Watts law. It is found that near the percolation threshold ρp∗, the decay of SISF to zero occurs via the power-law for sufficiently low wave-vectors. Our results establish that power-law divergence of the relaxation time τ as a function of density ρ occurs at a shape-dependent critical density ρc above the percolation threshold ρp∗. In the case of k-mers, the critical density ρc cannot be distinguished from the closest packing limit ρCPL⪅1. For other objects, the critical density ρc is usually below the jamming limit ρjam.

Percolation in random sequential adsorption of extended objects on a triangular lattice

The percolation aspect of random sequential adsorption of extended objects on a triangular lattice is studied by means of Monte Carlo simulations. The depositing objects are formed by self-avoiding lattice steps on the lattice. Jamming coverage θ{jam}, percolation threshold θ{p}, and their ratio θ{p}/θ{jam} are determined for objects of various shapes and sizes. We find that the percolation threshold θ{p} may decrease or increase with the object size, depending on the local geometry of the objects. We demonstrate that for various objects of the same length, the threshold θ{p} of more compact shapes exceeds the θ{p} of elongated ones. In addition, we study polydisperse mixtures in which the size of line segments making up the mixture gradually increases with the number of components. It is found that the percolation threshold decreases, while the jamming coverage increases, with the number of components in the mixture.

Surface integration approach: A new technique for evaluating geometry dependent forces between objects of various geometry and a plate

We present a new approach, which can be considered as a generalization of the Derjaguin approximation, that provides exact means to determine the force acting between a three-dimensional body of any shape and a half-space mutually interacting via pairwise potentials. Using it, in the cases of the Lennard-Jones, standard and the retarded (Casimir) van der Waals interactions we derive exact expressions for the forces between a half-space or a slab of finite thickness and an ellipsoid in a general orientation, which in the simplest case reduces to a sphere, a tilted fully elliptic torus, and a body obtained via rotation of a single loop generalized Cassini oval, a particular example of which mimics the shape of a red blood cell. The results are obtained for the case when the object is separated from the plane via a non-polar continuous medium that can be gas, liquid or vacuum. Specific examples of biological objects of various shapes interacting with a plate like substrates are also considered.

Simulation study of anisotropic random sequential adsorption of extended objects on a triangular lattice

The properties of the anisotropic random sequential adsorption (RSA) of objects of various shapes on a two-dimensional triangular lattice are studied numerically by means of Monte Carlo simulations. The depositing objects are formed by self-avoiding lattice steps, whereby the first step determines the orientation of the object. Anisotropy is introduced by positing unequal probabilities for orientation of depositing objects along different directions of the lattice. This probability is equal p or (1-p)/2, depending on whether the randomly chosen orientation is horizontal or not, respectively. Approach of the coverage θ(t) to the jamming limit θ(jam) is found to be exponential θ(jam)-θ(t)is proportional to exp(-t/σ), for all probabilities p. It was shown that the relaxation time σ increases with the degree of anisotropy in the case of elongated and asymmetrical shapes. However, for rounded and symmetrical shapes, values of σ and θ(jam) are not affected by the presence of anisotropy. We finally analyze the properties of the anisotropic RSA of polydisperse mixtures of k-mers. Strong dependencies of the parameter σ and the jamming coverage θ(jam) on the degree of anisotropy are obtained. It is found that anisotropic constraints lead to the increased contribution of the longer k-mers in the total coverage fraction of the mixture.

Distributed-Controlled Multiagent Mobile Platform with Digital Actuation Concept for Space Applications

This paper describes an architecture for a multiagent robotic system that consists of a number of identical units. The homogeneous units are mechanically connected to construct a mobile platform named a “multiagent transportation (MAT) system.” Every unit has its local controller that communicates only with its adjacent units. This basic configuration of supervisorless structure affirmatively confines the dependence of each unit to a local area, and therefore any unit can be removed from or added into any part of a MAT system regardless of the timing and without disturbing the performance of the whole system. This flexibility of configuration significantly contributes to easy maintenance of units, such as battery charging or hot-replacing for faulty units. Utilizing this flexibility, MAT systems are able to adapt to a variety of tasks including transportation application and to target objects of various shapes and range of mass. These characteristics of MAT systems are the strong advantages for mobile rob...

Stabilization of Nanoparticle Shells by Competing Interactions

We demonstrate a mechanism to intrinsically stabilize a hollow shell composed of individual nanoparticles. Using Monte Carlo simulations, we show that if nanoparticles that interact via short-range attraction and long-range repulsion are assembled on a template, the resulting shell can be stabilized upon the removal of the template. The interplay of attractive and repulsive interactions provides energy barriers that dynamically arrest the particles and stabilize the shell. We present a well-defined stability region in the interaction parameters space. We find a transition from single layered to multilayered stable shell by increasing the range of attraction, and show that the mechanism is not limited to spherical shells but can also be extended to stabilize nonspherical shells such as torus shells. This study can potentially be useful in understanding and engineering the assembly of nanoparticles into hollow objects of various shapes.

Analysis/Synthesis of Sounds Generated by Sustained Contact Between Rigid Objects

This paper introduces an analysis/synthesis scheme for the reproduction of sounds generated by sustained contact between rigid bodies. This scheme is rooted in a Source/Filter decomposition of the sound where the filter is described as a set of poles and the source is described as a set of impulses representing the energy transfer between the interacting objects. Compared to single impacts, sustained contact interactions like rolling and sliding make the estimation of the parameters of the Source/Filter model challenging because of two issues. First, the objects are almost continuously interacting. The second is that the source is generally unknown and has therefore to be modeled in a generic way. In an attempt to tackle those issues, the proposed analysis/synthesis scheme combines advanced analysis techniques for the estimation of the filter parameters and a flexible model of the source. It allows the modeling of a wide range of sounds. Examples are presented for objects of various shapes and sizes, rolling or sliding over plates of different materials. In order to demonstrate the versatility of the approach, the system is also considered for the modeling of sounds produced by percussive musical instruments.

청소 로봇을 위한 특징점 맵 기반의 전 영역 청소 알고리즘

청소 로봇의 중요한 기술 중 하나는 커버리지 성능이다. 대부분의 가정용 청소 로봇들은 로봇의 크기나 제작 비용 때문에 로봇을 구성하는 시스템 구성에 제약을 받게 된다. 이러한 이유 때문에 청소 로봇의 가장 중요한 요소인 커버리지 성능을 높이는데 필요한, 위치 인식이나 맵 구성을 위한 기존의 알고리즘들을 쉽게 적용할 수가 없다. 본 논문에서는 청소 로봇을 위한 두 가지 문제에 초점을 맞추어 이를 해결 할 수 있는 방안을 제시한다. 먼저 계산 량을 줄여 저가형 시스템을 구성할 수 있어야 한다. 이를 위해 청소 환경을 단순화 하는 형태로 변화 시켜 위치 인식과 특징점 맵을 구성하는데 필요한 계산량을 줄이는 방법을 제안한다. 두 번째로 청소로봇에 사용하는 센서들의 성능이 매우 제한적이다. 청소 로봇에 가장 많이 사용되는 센서는 초음파 센서와 적외선 센서이다. 초음파 센서의 경우에는 로봇의 크기나 구조적인 문제 때문에 측정 범위가 제한되고, 적외선의 경우엔 비용 문제와 센서 자체가 가지고 있는 측정 범위에 대한 문제에 의해 근거리 측정용 센서만을 사용한다. 이러한 센서들의 성능을 고려한 특징점 추출 방법을 설명하고 이를 이용한 맵 구성과 청소 영역 분할에 대한 방법을 제안한다. 본 논문에서 제안된 전 영역 청소를 위한 알고리즘들은 실제 판매되는 청소 로봇에 적용하여, 그 성능을 검증한다. The coverage ability is one of essential techniques for the Robotic Vacuum Cleaner (RVC). Most of the RVCs rely on random or regular pattern movement to cover a target space due to the technical difficulties to implement localization and map and constraints of hardwares such as controller and sensors. In this paper, we consider two main issues which are low computational load and using sensors with very limited sensing capabilities. First, in our approach, computing procedures to build map and detect the RVC's position are minimized by simplifying data obtained from sensors. To reduce computational load, it needs simply presenting an environment with objects of various shapes. Another isuue mentioned above is regarded as one of the most important problems in our approach, because we consider that many RVCs use low-cost sensor systems such as an infrared sensor or ultrasonic sensor with limited capabilities in limited range, detection uncertainty, measurement noise, etc. Methods presented in this paper are able to apply to general RVCs equipped with these sensors. By both simulation and real experiment, we evaluate our method and verify that the proposed method guarantees a complete coverage.

A new grasp quality measure considering the physical limits of robot hands

In this article, we introduce the extended grasp wrench space (GWS) to identify the applied location and the magnitude of the critical external wrench. We jointly use the task wrench space (TWS), which is made up of all possible external wrenches produced from the unit normal force to the surface points of the grasped object (i.e., the object wrench space [OWS]). In the extended GWS, the torque bound of each joint of the robot hand is considered to determine the grasp capability. Through convexity analysis and a linear programming technique, we propose a new way of obtaining an enhanced grasp measure which shows a clear physical meaning. We verify the proposed grasp analysis and quality measure using a visual grasp simulator and polygonal objects of various shapes.