96 research outputs found

    A bibliography on parallel and vector numerical algorithms

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    This is a bibliography of numerical methods. It also includes a number of other references on machine architecture, programming language, and other topics of interest to scientific computing. Certain conference proceedings and anthologies which have been published in book form are listed also

    Approaches to Conflict-free Replicated Data Types

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    Conflict-free Replicated Data Types (CRDTs) allow optimistic replication in a principled way. Different replicas can proceed independently, being available even under network partitions, and always converging deterministically: replicas that have received the same updates will have equivalent state, even if received in different orders. After a historical tour of the evolution from sequential data types to CRDTs, we present in detail the two main approaches to CRDTs, operation-based and state-based, including two important variations, the pure operation-based and the delta-state based. Intended as a tutorial for prospective CRDT researchers and designers, it provides solid coverage of the essential concepts, clarifying some misconceptions which frequently occur, but also presents some novel insights gained from considerable experience in designing both specific CRDTs and approaches to CRDTs.Comment: 36 page

    An Analytical Approach to Programs as Data Objects

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    This essay accompanies a selection of 32 articles (referred to in bold face in the text and marginally marked in the bibliographic references) submitted to Aarhus University towards a Doctor Scientiarum degree in Computer Science.The author's previous academic degree, beyond a doctoral degree in June 1986, is an "Habilitation à diriger les recherches" from the Université Pierre et Marie Curie (Paris VI) in France; the corresponding material was submitted in September 1992 and the degree was obtained in January 1993.The present 32 articles have all been written since 1993 and while at DAIMI.Except for one other PhD student, all co-authors are or have been the author's students here in Aarhus

    Aeronautical engineering: A continuing bibliography with indexes (supplement 210)

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    This bibliography lists 409 reports, articles and other documents introduced into the NASA scientific and technical information system in January 1987

    Systems reliability issues for future aircraft

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    The reliability of adaptive controls for future aircraft are discussed. The research, formulation, and experimentation for improved aircraft performance are considered

    Solution of partial differential equations on vector and parallel computers

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    The present status of numerical methods for partial differential equations on vector and parallel computers was reviewed. The relevant aspects of these computers are discussed and a brief review of their development is included, with particular attention paid to those characteristics that influence algorithm selection. Both direct and iterative methods are given for elliptic equations as well as explicit and implicit methods for initial boundary value problems. The intent is to point out attractive methods as well as areas where this class of computer architecture cannot be fully utilized because of either hardware restrictions or the lack of adequate algorithms. Application areas utilizing these computers are briefly discussed

    Investigations into the design of a wheelchair-mounted rehabilitation robotic manipulator

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    This research describes the steps towards the development of a low-cost wheelchair-mounted manipulator for use by the physically disabled and elderly. A detailed review of world rehabilitation robotics research has been conducted, covering fifty-six projects. This identified the main areas of research, their scope and results. From this review, a critical investigation of past and present wheelchair-mounted robotic arm projects was undertaken. This led to the formulation of the key design parameters in a final design specification. The results of a questionnaire survey of fifty electric wheelchair users is presented, which has for the first time established the needs and abilities of this disability group. An analysis of muscle type actuators, which mimic human muscle, is presented and their application to robotics, orthotics and prosthetics is given. A new type of rotary pneumatic muscle actuator, the flexator, is introduced and through extensive testing its performance characteristics elucidated. A review of direct-drive rotary pneumatic, hydraulic and electrical actuators has highlighted their relative performance characteristics and has rated their efficiency in terms of their peak torque to motor mass ratio, Tp/MM. From this, the flexator actuator has been shown to have a higher Tp/MM ratio than most conventional actuators. A novel kinematic arrangement is presented which combines the best features of the SCARA and vertically articulated industrial robot geometries, to form the 'Scariculated' arm design. The most appropriate actuator for each joint of this hybrid manipulator was selected, based on the criteria of high Tp/MM ratio, low cost, safety and compatibility. The final design incorporates conventional pneumatic linear double-acting cylinders, a vane type rotary actuator, two dual flexator actuators, and stepping motors for the fme control of the wrist/end effector. An ACSL simulation program has been developed which uses mass flow rate equations, based on one-dimensional compressible flow theory and suppressed critical pressure ratios, to simulate the dual flexator actuator. Theoretical and empirical data is compared and shows a high degree of correlation between results. Finally, the design and development work on two prototypes is discussed. The latest prototype consists of a five-axis manipulator whose pneumatic joints are driven by pulse width modulated solenoid valves. An 8051 microprocessor with proportional error feedback modilles the mark to space ratio of the PWM signal in proportion to the angular error of the joints. This enables control over individual joint speeds, reprogrammable memory locations and position monitoring of each joint. The integration of rehabilitation robotic manipulators into the daily lives of the physically disabled and elderly will significantly influence the role of personal rehabilitation in the next century

    Aeronautical engineering: A continuing bibliography with indexes (supplement 195)

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    This bibliography lists 389 reports, articles and other documents introduced into the NASA scientific and technical information system in December 1985

    Technology for large space systems: A bibliography with indexes (supplement 11)

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    This bibliography contains 539 abstracts of reports, articles and other documents introduced into the NASA scientific and technical information system between January 1, 1984 and December 31, 1984. Abstracts are arranged in the following categories: systems; analysis and design techniques; structural concepts; structural and thermal analysis; structural dynamics and control; electronics; advanced materials; assembly concepts; propulsion; and miscellaneous. Subject, personal author, corporate source, contract number, report number, and accession number indexes are listed
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