This paper presents a novel approach to on-line, robot-motion planning for moving-object interception. The proposed approach utilizes a navigation-based technique, which is robust and computationally efficient for the...
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This paper presents a novel approach to on-line, robot-motion planning for moving-object interception. The proposed approach utilizes a navigation-based technique, which is robust and computationally efficient for the interception of fast-maneuvering objects. Navigation-based techniques were originally developed for the control of missiles tracking free-flying targets. Unlike a missile, however, the end-effector of a robotic arm is connected to the ground, via a number of links and joints, subject to kinematic and dynamic constraints. Also, unlike a missile, the velocity of the robot and the moving object must be matched for a smooth grasp, thus, a hybrid interception scheme, which combines a navigation-based interception technique with a conventional trajectory tracking method is proposed herein for intercepting fast-maneuvering objects. The implementation of the proposed technique is discussed via numerous simulation examples. (C) 1999 Elsevier Science B.V. All rights reserved.
The Social Exclusion Unit's Report Bridging the Gap has had a major influence on the British government's policy towards socially excluded young people. This article argues, however, that the Report contains f...
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The Social Exclusion Unit's Report Bridging the Gap has had a major influence on the British government's policy towards socially excluded young people. This article argues, however, that the Report contains fundamental contradictions in its analysis of non-participation in learning and the solutions proposed. Despite appearing to re-instate a concern for the social, it locates the causes of non-participation primarily within individuals and their personal deficits. Yet it denies individuality and diversity by representing the socially excluded as stereotyped categories. In a flawed move, the Report presents non-participation not just in correlation to a raft of other social problems, but as cause to their effect. Deep-seated structural inequalities are rendered invisible, as social exclusion is addressed through a strongly individualistic strategy based on personal agency. At the same time, measures to enhance individual agency, notably the new 'ConneXions' service, are formulated within a prescriptive structural framework. Structure and agency are thus reversed in current English policy approaches. While such approaches will doubtless assist some young people, there is a significant risk that they may make things worse for others.
This paper draws on the authors' experience of developing and presenting an Open University Masters level course: guidance and Counselling in Learning. Questions of 'who is the audience?' and 'what is ...
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This paper draws on the authors' experience of developing and presenting an Open University Masters level course: guidance and Counselling in Learning. Questions of 'who is the audience?' and 'what is the model of professional development?' are explored, surfacing the diversity of contexts for guidance practices and the assumptions about the relationship between theory and practice which are embedded in various approaches to professional development. The discursive approach adopted by the course team, involving students in processes of 'mapping', 'locating' and 'translating' in and between discourses of guidance, is outlined, suggesting that this provides a means of finessing the traditional theory-practice binary. A small-scale evaluation of the impact of studying the course was carried out on a sample of the first cohort of students. Data from this are used to illustrate some effects of the discursive approach on the ways in which students talk about their learning and their practice.
A key feature of the central nervous system of most higher organisms is their bilateral symmetry about the midline, The specialised cells that lie at the midline have an essential role in regulating the axon guidance ...
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A key feature of the central nervous system of most higher organisms is their bilateral symmetry about the midline, The specialised cells that lie at the midline have an essential role in regulating the axon guidance decisions of both neurons that project axons across the midline and those that project on one side. The midline cells produce both attractive and repellent short- and long-range signals to guide axonal growth. The axons themselves express specific receptors that can be dynamically regulated in response to midline-derived signals. In this way, axons extend toward or away from the midline and those that do cross change their behaviour to respond to longitudinal signals on the contralateral side.
The method described here explains a simple protocol for how to prepare dissociated Zebrafish spinal neuron cultures. The neurons grow fast in a simple culture medium and at room temperature. Considering the advantage...
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The method described here explains a simple protocol for how to prepare dissociated Zebrafish spinal neuron cultures. The neurons grow fast in a simple culture medium and at room temperature. Considering the advantages afforded by the optical transparency of the Zebrafish embryo combined with the powerful molecular perturbation techniques available, this technique has potential to further advance molecular analysis of axon growth and guidance.
Pollen tubes follow a well-defined path to deliver male gametes to female gametes, but the mechanisms they use to locate this path are poorly understood. The major hypothesis is (and long has been) that pollen tubes a...
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Pollen tubes follow a well-defined path to deliver male gametes to female gametes, but the mechanisms they use to locate this path are poorly understood. The major hypothesis is (and long has been) that pollen tubes are guided by chemical gradients and/or physical structures. Recently, parallels have been drawn between chemical mechanisms of guidance in pollen tubes and other cells, such as axons. These comparisons highlight a problem with the current models for pollen tube guidance, namely the distance over which chemical guidance is proposed to occur. Based on this new perspective, same models are either invalid or pollen tubes are uniquely responsive to chemical guidance cues.
作者：
Brown, JOpen Univ N
Regent Ctr Newcastle Upon Tyne NE3 3PW Tyne & Wear England
Recent developments have raised questions about the distinctiveness of guidance and whether its practice cart be separated from that of related professions. Those developments are reviewed. It is suggested that a dist...
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Recent developments have raised questions about the distinctiveness of guidance and whether its practice cart be separated from that of related professions. Those developments are reviewed. It is suggested that a distinctive position may be found by an examination of certain key features of guidance practice. One of these features is the role of information. Information is distinguished front informing. Tts nature is discussed, as is its use in practice by both clients and guidance practitioners.
The emphasis upon the creation of a culture of lifelong learning propels the issue of accessibility to guidance for adults into the limelight. The Careers Service and other careers guidance providers have demonstrated...
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The emphasis upon the creation of a culture of lifelong learning propels the issue of accessibility to guidance for adults into the limelight. The Careers Service and other careers guidance providers have demonstrated a commitment to all-age guidance in the absence of a coherent policy or resource framework. Following 'contracting out: Careers Services are wrestling with the ambiguities inherent in the 'private company-public service' equation. These are compounded by the continuing absence of clarity at policy level regarding the development of all-age guidance. The central question remains that of how a service, with benefits accruing to the individual, the community and the economy, is most appropriately funded and delivered.
The Video guidance Sensor (VGS), part of NASA's Automated Rendezvous and Capture program, was flown on Shuttle mission STS-95 in October of 1998 to test on-orbit the functional characteristics of the VGS. This was...
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ISBN:
(纸本)0819431818
The Video guidance Sensor (VGS), part of NASA's Automated Rendezvous and Capture program, was flown on Shuttle mission STS-95 in October of 1998 to test on-orbit the functional characteristics of the VGS. This was the second flight of the VGS (the first flight was in 1997 on STS-87), and this time long-range tracking data was gathered during the experiment. The flight experiment sensor was designed to operate from 1.5 meter range out to 110 meter range, with a field-of-view of 16 by 21 degrees. The VGS tracked its target at a 5 Hz rate and returned 6-degree-of-freedom information on the target's position and attitude relative to the sensor. The VGS was mounted in the Shuttle cargo bay, and its target was mounted on the Spartan spacecraft being carried on this mission. The orbital testing of the VGS included operations with the target on the Shuttle's Remote Manipulator System (RMS) at the start of the 10-day mission, long-range data during the Shuttle rendezvous with the Spartan two days later, and some more RMS operations later in the mission. The data returned from the orbital testing included VGS diagnostics, acquisition, and tracking data, RMS positions, hand-held laser range data, tapes of the data from the VGS video camera, and orbital positioning data from the Spartan and the Shuttle to allow correlation of the VGS data with orbital best-estimate-of-truth data. The Video guidance Sensor performed well in all phases of the testing, and the VGS is being incorporated into the ground testing of a complete automated rendezvous and docking system. Work on the development of the next generation VGS is continuing.
In order to increase the tactile sensing range and allow larger AGV speeds that result in larger vehicle stopping distances, the recently reported fibreoptic 'curvature gauges' sensitized to their geometric cu...
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ISBN:
(纸本)0819434256
In order to increase the tactile sensing range and allow larger AGV speeds that result in larger vehicle stopping distances, the recently reported fibreoptic 'curvature gauges' sensitized to their geometric curvature are arranged in loops around the AGV. When the AGV is driven into other objects (obstacles), these loops deform, resulting in the change of their curvature - which is registered. While many different types of bumpers and whiskers have been used in the past for a similar purpose, the key difference here is that no intermediate mechanical elements are employed to either transfer the impact loads onto the sensitive element or provide compliance to it. Optical fibres themselves provide both functions simultaneously. As a result, tactility is achieved within a comparatively large range extending over 10 cm. Throughout this range, virtually no reaction forces are generated with the impacting body. The range mentioned is on top of the one provided by the more traditional elastic bumper the optical fibres are mounted on.
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