735 research outputs found
Basic Issues and Current Status of Parallel Computing -- 1995
The best enterprises have both a compelling need pulling them forward and an innovative technological solution pushing them on. In high-performance computing, we have the need for increased computational power in many applications and the inevitable long-term solution is massive parallelism. In the short term, the relation between pull and push may seem unclear as novel algorithms and software are needed to support parallel computing. However, eventually parallelism will be present in all computers -- including those in your children\u27s video game, your personal computer or workstation, and the central supercomputer
THE DEVELOPMENT OF NOVEL TECHNIQUES FOR CHARACTERISATION OF MARINE ZOOPLANKTON OVER VERY LARGE SPATIAL SCALES
Marine zooplankton play an important role in the transfer of CO2 from the
atmosphere/ocean system to deeper waters and the sediments. They also provide food for
much of the world's fish stocks and in some areas of the ocean depleted of nutrients they
sustain phytoplankton growth by recycling nutrients. They therefore have a profound
effect on the carbon cycle and upon life in the oceans. There is a perceived lack of
information about global distributions of zooplankton needed to validate ecosystems
dynamics models, and the traditional methods of survey are inadequate to provide this
information. There is a need to develop new technologies for the large scale survey of
zooplankton, which should provide data either suitable for quick and easy subsequent
processing, or better still, processed in real time.
New technologies for large scale zooplankton survey fall into three main categories:
acoustic, optical and video. No single method is capable of providing continuous real
time data at the level of detail required. A combination of two of the new technologies
(optical and video) has the potential to provide broad scale data on abundance, size and
species distributions of zooplankton routinely, reliably, rapidly and economically. Such a
combined method has been developed in this study. The optical plankton counter (OPC)
is a fairly well established instrument in marine and freshwater zooplankton survey. A
novel application of the benchtop version of this instrument (OPC-IL) for real time data
gathering at sea over ocean basin scales has been developed in this study. A new
automated video zooplankton analyser (ViZA) has been designed and developed to
operate together with the OPC-IL. The two devices are eventually to be deployed in
tandem on the Undulating Oceanographic Recorder (UOR) for large scale ocean survey
of zooplankton.
During the initial development of the system, the two devices are used in benchtop flow
through mode using the ship's uncontaminated sea water supply. The devices have been
deployed on four major oceanographic cruises in the North and South Atlantic, covering
almost 40,000 km. of transect. Used in benchtop mode, it has been shown that the OPC
can simply and reliably survey thousands of kilometres of ocean surface waters for
zooplankton abundance and size distribution in the size range 250|im. to 11.314 mm. in
real time. The ViZA system can add the dimension of shape to the OPC size data, and
provide supporting data on size distributions and abundance. Sampling rate in
oligotrophic waters, and image quality problems are two main limitations to current
ViZA performance which must be addressed, but where sufficient abundance exists and
good quality images are obtained, the initial version of the ViZA system is shown to be
able reliably to classify zooplankton to six major groups.
The four deployments have shown that data on zooplankton distributions on oceanic
scales can be obtained without the delays and prohibitive costs associated with sample
analysis for traditional sampling methods. The results of these deployments are
presented, together with an assessment of the performance of the system and proposals
for improvements to meet the requirements specified before a fiill in-situ system is
deployed.Plymouth Marine Laborator
Spacelab data analysis and interactive control study
The study consisted of two main tasks, a series of interviews of Spacelab users and a survey of data processing and display equipment. Findings from the user interviews on questions of interactive control, downlink data formats, and Spacelab computer software development are presented. Equipment for quick look processing and display of scientific data in the Spacelab Payload Operations Control Center (POCC) was surveyed. Results of this survey effort are discussed in detail, along with recommendations for NASA development of several specific display systems which meet common requirements of many Spacelab experiments
Network control for a multi-user transputer-based system.
A dissertation submitted to the Faculty of Engineering, University of the
Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of
Master of Science in EngineeringThe MC2/64 system is a configureable multi-user transputer- based system which was
designed using a modular approach. The MC2/64 consists of MC2 Clusters which are
connected using a modified Clos network. The MC2 Clusters were designed and
realised as completely configurable modules using and extending an algorithm based on
Eulerian cycles through a requested graph. This dissertation discusses the configuration
algorithm and the extensions made to the algorithm for the MC2 Clusters.
The total MC2/64 system is not completely configurable as a MC2 Cluster releases only
a limited number of links for inter-cluster connections. This dissertation analyses the
configurability of MC2/64, but also presents algorithms which enhance the usability of
the system from the user's point of view.
The design and the implementation of the network control software are also submitted
as topics in this dissertation. The network control software must allow multiple users to
use the system, but without them influencing each other's transputer domains.
This dissertation therefore seeks to give an overview of network control problems and
the solutions implemented in current MC2/64 systems. The results of the research
done for this dissertation will hopefully aid in the design of future MC2 systems which
will provide South Africa with much needed, low cost, high performance computing
power.Andrew Chakane 201
From Piz Daint to the Stars: Simulation of Stellar Mergers using High-Level Abstractions
We study the simulation of stellar mergers, which requires complex
simulations with high computational demands. We have developed Octo-Tiger, a
finite volume grid-based hydrodynamics simulation code with Adaptive Mesh
Refinement which is unique in conserving both linear and angular momentum to
machine precision. To face the challenge of increasingly complex, diverse, and
heterogeneous HPC systems, Octo-Tiger relies on high-level programming
abstractions.
We use HPX with its futurization capabilities to ensure scalability both
between nodes and within, and present first results replacing MPI with
libfabric achieving up to a 2.8x speedup. We extend Octo-Tiger to heterogeneous
GPU-accelerated supercomputers, demonstrating node-level performance and
portability. We show scalability up to full system runs on Piz Daint. For the
scenario's maximum resolution, the compute-critical parts (hydrodynamics and
gravity) achieve 68.1% parallel efficiency at 2048 nodes.Comment: Accepted at SC1
Proceedings of the Fifth International Mobile Satellite Conference 1997
Satellite-based mobile communications systems provide voice and data communications to users over a vast geographic area. The users may communicate via mobile or hand-held terminals, which may also provide access to terrestrial communications services. While previous International Mobile Satellite Conferences have concentrated on technical advances and the increasing worldwide commercial activities, this conference focuses on the next generation of mobile satellite services. The approximately 80 papers included here cover sessions in the following areas: networking and protocols; code division multiple access technologies; demand, economics and technology issues; current and planned systems; propagation; terminal technology; modulation and coding advances; spacecraft technology; advanced systems; and applications and experiments
Features and Functions: Decomposing the Neural and Cognitive Bases of Semantic Composition
In this dissertation, I present a suite of studies investigating the neural and cognitive bases of semantic composition. First, I motivate why a theory of semantic combinatorics is a fundamental desideratum of the cognitive neuroscience of language. I then introduce a possible typology of semantic composition: one which involves contrasting feature-based composition with function-based composition. Having outlined several different ways we might operationalize such a distinction, I proceed to detail two studies using univariate and multivariate fMRI measures, each examining different dichotomies along which the feature-vs.-function distinction might cleave. I demonstrate evidence that activity in the angular gyrus indexes certain kinds of function-/relation-based semantic operations and may be involved in processing event semantics. These results provide the first targeted comparison of feature- and function-based semantic composition, particularly in the brain, and delineate what proves to be a productive typology of semantic combinatorial operations. The final study investigates a different question regarding semantic composition: namely, how automatic is the interpretation of plural events, and what information does the processor use when committing to either a distributive plural event (comprising separate events) or a collective plural event (consisting of a single joint event)
Aspects of an open architecture robot controller and its integration with a stereo vision sensor.
The work presented in this thesis attempts to improve the performance of industrial robot systems in a flexible manufacturing environment by addressing a number of issues related to external sensory feedback and sensor integration, robot kinematic positioning accuracy, and robot dynamic control performance. To provide a powerful control algorithm environment and the support for external sensor integration, a transputer based open architecture robot controller is developed. It features high computational power, user accessibility at various robot control levels and external sensor integration capability. Additionally, an on-line trajectory adaptation scheme is devised and implemented in the open architecture robot controller, enabling a real-time trajectory alteration of robot motion to be achieved in response to external sensory feedback. An in depth discussion is presented on integrating a stereo vision sensor with the robot controller to perform external sensor guided robot operations. Key issues for such a vision based robot system are precise synchronisation between the vision system and the robot controller, and correct target position prediction to counteract the inherent time delay in image processing. These were successfully addressed in a demonstrator system based on a Puma robot. Efforts have also been made to improve the Puma robot kinematic and dynamic performance. A simple, effective, on-line algorithm is developed for solving the inverse kinematics problem of a calibrated industrial robot to improve robot positioning accuracy. On the dynamic control aspect, a robust adaptive robot tracking control algorithm is derived that has an improved performance compared to a conventional PID controller as well as exhibiting relatively modest computational complexity. Experiments have been carried out to validate the open architecture robot controller and demonstrate the performance of the inverse kinematics algorithm, the adaptive servo control algorithm, and the on-line trajectory generation. By integrating the open architecture robot controller with a stereo vision sensor system, robot visual guidance has been achieved with experimental results showing that the integrated system is capable of detecting, tracking and intercepting random objects moving in 3D trajectory at a velocity up to 40mm/s
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