| 1. |
- Johnsson, Eva, et al.
(author)
-
Den psykosociala integrationens fält.
- 2019
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In: Det professionella landskapets framväxt. - 9789144122052 ; , s. 261-331
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Book chapter (other academic/artistic)
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| 2. |
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| 3. |
- Abdullah, Matin, et al.
(author)
-
SimDB: A Problem Solving Environment for Molecular Dynamics Simulation and Analysis
- 2000
-
Conference paper (peer-reviewed)abstract
- The design of a software environment, SimDB, for molecular dynamics simulation and analysis is presented as an example of virtual laboratories enabled by high-speed networks connecting substantial computing and storage resources with more modest local compuation and visualization resources available to research groups. SimDB includes large-scale, dynamic, distributed data repositories. The simulated data sets, trajectories, are usually interpreted through reduced data sets, processed data sets, calculated by analysis functions. Both trajectory data and processed data are saved, but in differnt data bases, with processed data bases having several smaller objects for each trajectory. A browser based user interface with a well defined API allows for a wide array of analysis functions. Analysis functions are executed only if the requested analysis result is not available. The ability to incorporate user defined functions is a critical feature of SimDB.
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| 4. |
- Ahsant, Mehran, et al.
(author)
-
Dynamic, Context-Aware, Least-Privilege Grid Delegation
- 2007
-
In: 8th IEEE/ACM International Conference on Grid Computing. - New York : IEEE. - 9781424415595 ; , s. 209-216
-
Conference paper (peer-reviewed)abstract
- Performing delegation in large scale, dynamic and distributed environments with large numbers of shared resources is more challenging than inside local administrative domains. In dynamic environments like Grids, on one hand, delegating a restricted set of rights reduces exposure to attack but also limits the flexibility and dynamism of the application; on the other hand, delegating all rights provides maximum flexibility but increases exposure. This issue has not yet been adequately addressed by current Grid security mechanisms and is becoming a very challenging and crucial issue for future Grid development. Therefore, providing an effective delegation mechanism which meets the requirements of the least privilege principle is becoming an essential need. Furthermore, we are witnessing a phenomenal increase in the automation of organizational tasks and decision making, as well as the computerization of information related services, requiring automated delegation mechanisms. In order to meet these requirements we introduce an Active Delegation Framework which extends our previous work on on-demand delegation, making it context-aware. The framework provides a just-in-time, restricted and dynamic delegation mechanism for Grids. In this paper we describe the development of this framework and its implementation and integration with the Globus Toolkit.
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| 5. |
- Ahsant, Mehran, 1974-
(author)
-
On-demand Restricted Delegation : A Framework for Dynamic, Context-Aware, Least-Privilege Delegation in Grids
- 2009
-
Doctoral thesis (other academic/artistic)abstract
- In grids, delegation is a key facility that can be used to authenticate and authorize requests on behalf of disconnected users. In current grid systems,delegation is either performed dynamically, in an unrestricted manner, or by a secure but static method. Unfortunately, the former compromises security and the latter cannot satisfy the requirements of dynamic grid application execution. Therefore, development of a delegation framework that enables a restricted and flexible delegation mechanism becomes increasingly urgent as grids are adopted by new communities and grow in size. The main barriers in development of such a mechanism are the requirements for dynamic execution of grid applications, which make it difficult to anticipate required access rights for completing tasks in advance. Another significant architectural requirement in grids is federated security and trust. A considerable barrier to achieving this is cross-organizational authentication and identification. Organizations participating in Virtual Organizations (VOs) may use different security infrastructures that implement different protocols for authentication and identification; thus, there exists a need to provide an architectural mechanism for lightweight, rapid and interoperable translation of security credentials from an original format to a format understandable by recipients. This thesis contributes the development of a delegation framework that utilizes a mechanism for determining and acquiring only required rights and credentials for completing a task, when they are needed. This is what we call an on-demand delegation framework that realizes a bottom-up delegation model and provides a just-in-time acquisition of rights for restricted and dynamic delegation. In this thesis, we further contribute the development of a credential mapping mechanism using off-the-shelf standards and technologies. This mechanism provides support for an on-the-fly exchange of different types of security credentials used by the security mechanisms of existing grids.
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| 6. |
- Ahsant, Mehran, et al.
(author)
-
Toward An On-demand Restricted Delegation Mechanism for Grids
- 2006
-
In: 2006 7TH IEEE/ACM INTERNATIONAL CONFERENCE ON GRID COMPUTING. - New York : IEEE. - 9781424403431 ; , s. 152-159
-
Conference paper (peer-reviewed)abstract
- Grids are intended to enable cross-organizationalinteractions which makes Grid security a challenging and nontrivialissue. In Grids, delegation is a key facility that canbe used to authenticate and authorize requests on behalf ofdisconnected users. In current Grid systems there is a tradeoffbetween flexibility and security in the context of delegation.Applications must choose between limited or full delegation: onone hand, delegating a restricted set of rights reduces exposure toattack but also limits the flexibility/dynamism of the application;on the other hand, delegating all rights provides maximumflexibility but increases exposure. In this paper, we propose anon-demand restricted delegation mechanism, aimed at addressingthe shortcomings of current delegation mechanisms by providingrestricted delegation in a flexible fashion as needed for Grid applications.This mechanism provides an ontology-based solutionfor tackling one the most challenging issues in security systems,which is the principle of least privileges. It utilizes a callbackmechanism, which allows on-demand provisioning of delegatedcredentials in addition to observing, screening, and auditingdelegated rights at runtime. This mechanism provides supportfor generating delegation credentials with a very limited andwell-defined range of capabilities or policies, where a delegatoris able to grant a delegatee a set of restricted and limited rights,implicitly or explicitly.
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| 7. |
- Ali, Ayaz, et al.
(author)
-
Adaptive Computation of Self Sorting In-place FFTs on Hierarchical Memory Architectures
- 2007
-
In: HIGH PERFORMANCE COMPUTING AND COMMUNICATIONS, PROCEEDINGS. - 9783540754435 ; , s. 372-383
-
Conference paper (peer-reviewed)abstract
- Computing ”in-place and in-order”FFT poses a very difficult problem on hierarchical memory architectures where data movement can seriously degrade the performance. In this paper we present recursive formulation of a self sorting in-place FFT algorithm that adapts to the target architecture. For transform sizes where an in-place, in-order execution is not possible, we show how schedules can be constructed that use minimum work-space to perform the computation efficiently. In order to express and construct FFT schedules, we present a context free grammar that generates the FFT Schedule Specification Language. We conclude by comparing the performance of our in-place in-order FFT implementation with that of other well known FFT libraries. We also present a performance comparison between the out-of-place and in-place execution of various FFT sizes.
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| 8. |
- Ali, Ayaz, et al.
(author)
-
Empirical Auto-tuning Code Generator for FFT and Trigonometric Transforms
- 2007
-
Conference paper (peer-reviewed)abstract
- We present an automatic, empirically tuned code genenrator for Real/Complex FFT and Trigonometric Transforms. The code generator is part of an adaptive and portable FFT computation framework - UHFFT. Performance portability over varying architectures is achieved by generating highly optimized set of straight line C codelets (micro-kernel) that adapt to the microprocessor architecture. The tuning is performed by generating several variants of same size codelet with different combinations of optimization parameters. The variants are iteratively compiled and evaluated to find the best implementation on a given platform. Apart from minimizing the operation count, the code generator optimizes for access pattern, register blocking, instruction schedule and structure of arrays. We present details of the optimizations conducted at several stages and the performance gain at each of those levels. We conclude the paper with discussion of the overall performance improvements due to this aggressive approach to generating optimized FFT kernels.
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| 9. |
- Ali, Ayaz, et al.
(author)
-
Scheduling FFT Computation on SMP and Multi-core Systems
- 2007
-
In: Proceedings of the 21st annual international conference on Supercomputing. - New York, NY, USA : ACM. ; , s. 293-301
-
Conference paper (peer-reviewed)abstract
- Increased complexity of memory systems to ameliorate the gap between the speed of processors and memory has made it increasingly harder for compilers to optimize an arbitrary code within a palatable amount of time. With the emergence of multicore (CMP), multiprocessor (SMP) and hybrid shared memory multiprocessor architectures, achieving high e ciency is becoming even more challenging. To address the challenge to achieve high e ciency in performance critical applications, domain speci c frameworks have been developed that aid the compilers in scheduling the computations. We have developed a portable framework for the Fast Fourier Transform (FFT) that achieves high e ciency by automatically adapting to various architectural features. Adapting to parallel architectures by searching through all the combinations of schedules (plans) is an expensive task, even when the search is conducted in parallel. In this paper, we develop heuristics to simplify the generation of better schedules for parallel FFT computations on CMP/SMP systems. We evaluate the performance of OpenMP and PThreads implementations of FFT on a number of latest architectures. The performance of parallel FFT schedules is compared with that of the best plan generated for sequential FFT and the speedup for di erent number of processors is reported. In the end, we also present a performance comparison between the UHFFT and FFTW implementations.
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| 10. |
- Andersson, Lennart, et al.
(author)
-
Praktikfall i reglerteknik - Råspritbränneriet i Nöbbelöv
- 1998
-
Reports (other academic/artistic)abstract
- During spring 1998 the course Industrial Case Studies in Control was given at the Department of Automatic Control in Lund. The course consisted of a project at an industry with control applications. This report considers a project at the crude alcohol distillery in Nöbbelöv, where the base product for the liquor Absolut Vodka is produced. The distillery had problems with fluctuations in the concentration of ethanol in the crude alcohol. The purpose of the project was to analyze the cause of the fluctuations, and if possibly eliminate it. The fluctuations were cause by an output limiter on a controller, and were relatively easily eliminated. To examine if control performance could be further improved, a series of experiments was carried out on the plant. The result of the experiments were then used to derive a simple process model, and a suggestion for new controller parameters.
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| 11. |
- Astermark, Jan, et al.
(author)
-
Blödarsjuka med HIV. Långsammare infektionsförlopp hos yngre och vid större förbrukning av faktorkoncentrat
- 1998
-
In: Läkartidningen. - 0023-7205. ; 95:1, s. 48-50
-
Journal article (peer-reviewed)abstract
- HIV disease progression and the effect of replacement therapy with clotting factor concentrates (CFCs) were studied in 100 Swedish haemophiliacs, mean age at seroconversion 29 years (range, 4-72). On average 16 years after seroconversion, 67 per cent of the patients had CD4+ cell counts of < 200 x 10(6)/l, 50 per cent had developed AIDS, and 58 per cent had died. HIV disease progression was significantly slower in those aged less than 28 (median age) at seroconversion (P = 0.004). Moreover, mortality was inversely correlated to total annual CFC consumption after adjustment for age and HIV-related therapy, i.e., Pneumocystis carinii prophylaxis and antiretroviral drugs (P = 0.014), but unrelated to the purity of the CFCs used. After adjustment for age, annual CFC consumption and HIV-therapy, prophylactic replacement therapy was not associated with significantly better survival than on-demand treatment. It is concluded that in HIV-positive haemophiliacs replacement therapy may have a beneficial effect on the immune system, and that CFC purity and the regimen (prophylaxis vs on-demand) would seem to be factors of minor importance.
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| 12. |
- Austin, S, et al.
(author)
-
Atmospheric Balloon Studies : A Collaboration Between Minority and Traditional Undergraduate and Graduate Institutions
- 2008
-
Conference paper (peer-reviewed)abstract
- The Minority University Consortium for Earth and Space Sciences (MUCESS), a collaboration among diverse minority institutions dedicated to increasing the number of underrepresented students pursuing professional and research careers in Earth and Atmospheric Science and Space Science, were informed that they had been funded by NSF for a faculty and student research opportunity in atmospheric science. Among the institutions only Medgar Evers College, City University of New York had a prior program in ozone monitoring and a bachelor's degree in environmental science. The funding provided an opportunity to strengthen the initial team with the addition of G. Morris, Valparaiso University and B. Lefer, University of Houston as both had an ongoing ozone research program. The grant enabled MEC to continue their activities and the University of Houston-Downtown to increase the number of launches per year. South Carolina State University is able to strengthen their support system and incorporate the activities into both their academic and outreach programs. The opportunity to partner with G. Morris and B. Lefer will enable the institutions to expand their ozonesonde launches to include both tropospheric and stratospheric ozone distribution and transport. Faculty student workshops will be an integral part of the program as the activity will increase the scientific knowledge of the participants. The program provides an opportunity for minority students to pursue studies in the geosciences and develop the skills and knowledge to pursue graduate degrees in the discipline.
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| 13. |
- Baillie, Clive, et al.
(author)
-
QCD with Dynamical Fermions on the Connection Machine
- 1989
-
Conference paper (peer-reviewed)abstract
- We have implemented Quantum Chromo-Dynamics (QCD) on the massively parallel Connection Machine in *Lisp. The code uses dynamical Wilson fermions and the Hybrid Monte Carlo Algorithm (HMCA) to update the lattice. We describe our program and give performance measurements for it. With no tuning or optimization, the code runs at approximately 500 to 1000 MFLOPS on a 64-K Connection Machine, model CM-2, depending on the VP ratio.
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| 14. |
- Berman, F., et al.
(author)
-
New grid scheduling and rescheduling methods in the GrADS Project
- 2005
-
In: International journal of parallel programming. - : Springer Science and Business Media LLC. - 0885-7458 .- 1573-7640. ; 33:3-Feb, s. 209-229
-
Journal article (peer-reviewed)abstract
- The goal of the Grid Application Development Software (GrADS) Project is to provide programming tools and an execution environment to ease program development for the Grid. This paper presents recent extensions to the GrADS software framework: a new approach to scheduling workflow computations, applied to a 3-D image reconstruction application; a simple stop/migrate/restart approach to rescheduling Grid applications, applied to a QR factorization benchmark; and a process-swapping approach to rescheduling, applied to an N-body simulation. Experiments validating these methods were carried out on both the GrADS MacroGrid (a small but functional Grid) and the MicroGrid (a controlled emulation of the Grid).
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| 15. |
- Berman, F., et al.
(author)
-
The GrADS project : Software support for high-level grid application development
- 2001
-
In: The international journal of high performance computing applications. - : SAGE Publications. - 1094-3420 .- 1741-2846. ; 15:4, s. 327-344
-
Journal article (peer-reviewed)abstract
- Advances in networking technologies will soon make it possible to use the global information infrastructure in a qualitatively different way-as a computational as well as an information resource. As described in the recent book The Grid: Blueprint for a New Computing Infrastructure, this Grid will connect the nation's computers, databases, instruments, and people in a seamless web of computing and distributed intelligence, which can be used in an on demand fashion as a problem-solving resource in many fields of human endeavor-and, in particular, science and engineering. The availability of grid resources will give rise to dramatically new classes of applications, in which computing resources are no longer localized but, rather, distributed, heterogeneous, and dynamic; computation is increasingly sophisticated and multidisciplinary; and computation is integrated into our daily lives and, hence, subject to stricter time constraints than at present. The impact of these new applications will be pervasive, ranging from new systems for scientific inquiry, through computing support for crisis management, to the use of ambient computing to enhance personal mobile computing environments. To realize this vision, significant scientific and technical obstacles must be overcome. Principal among these is usability. The goal of the Grid Application Development Software (GrADS) project is to simplify distributed heterogeneous computing in the same way that the World Wide Web simplified information sharing over the Internet. To that end, the project is exploring the scientific and technical problems that must be solved to make it easier for ordinary scientific users to develop, execute, and tune applications on the Grid. In this paper, the authors describe the vision and strategies underlying the GrADS project, including the base software architecture for grid execution and performance monitoring, strategies and tools for construction of applications from libraries of grid-aware components, and development of innovative new science and engineering applications that can exploit these new technologies to run effectively in grid environments.
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| 16. |
- Berntsson, Thore, 1947, et al.
(author)
-
Towards Sustainabel Oil Refinery - Pre-study for larger co-operation project
- 2008
-
Reports (other academic/artistic)abstract
- In this report, the Chalmers EnergiCentrum (CEC) presents the results of a pre-study commissioned by Preem relating to the effective production of future vehicle fuels.This pre-study was made up of three studies focusing on energy streamlining, the utilisation of waste heat and carbon-dioxide separation and biorefinement relating to the gasification and hydration of vegetable oils. One of the common starting points for these studies was the current situation at the Preem refineries in Göteborg and Lysekil from where the measurement data were obtained and analysed. The report summarises the knowledge situation based on current research in the individual technical fields. The results present some interesting future opportunities for developing the sustainable production of future vehicle fuels. The sections vary, as the areas that have been examined differ and the sections have been written by different people. The reports ends with some joint conclusions and a number of questions which could be included and answered in a more extensive future main study, as part of a developed research partnership between Preem and the Chalmers University of Technology. The preliminary results of this work were analysed with the client at workshops on 1 October and 29 November 2007. The report is written in English combined with an extensive summary in Swedish including a proposal on a future main study. The study was conducted by the Chalmers EnergiCentrum (CEC), in collaboration with a number of researchers in the CEC’s network. They included Thore Berntsson, Jessica Algehed, Erik Hektor and Lennart Persson Elmeroth, all from Heat and Power Technology, Börje Gevert, Chemical and Biological Engineering, Tobias Richards, Forest Products and Chemical Engineering, Filip Johnsson and Anders Lyngfelt, Energy Technology, and Per-Åke Franck and Anders Åsblad, CIT Industriell Energianalys AB. The client, Preem, was represented by Bengt Ahlén, Sören Eriksson, Johan Jervehed, Bertil Karlsson, Gunnar Olsson, Ulf Kuylenstierna, Stefan Nyström, Martin Sjöberg and Thomas Ögren. Tobias Richards was responsible for compiling the report and Bertil Pettersson was the project manager.
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| 17. |
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| 18. |
- Brickner, R.G, et al.
(author)
-
QCD on the Connection Machine: Beyond-Lisp
- 1991
-
In: Computer Physics Communications. - 0010-4655 .- 1879-2944. ; 65, s. 39-51
-
Journal article (peer-reviewed)abstract
- We report on the status of code development for a simulation of quantum chromodynamics (QCD) with dynamical Wilson fermions on the Connection Machine model CM-2. Our original code, written in * Lisp, gave performance in the near-GFLOPS range. We have rewritten the most time-consuming parts of the code in the low-level programming system CMIS, including the matrix multiply and the communication. Current versions of the code run at approximately 3.6 GFLOPS for the fermion matrix inversion, and we expect the next version to reach or exceed 5 GFLOPS.
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| 19. |
- Brunet, Jean-Philippe, et al.
(author)
-
All–to–All Broadcast with Applications on the Connection Machine
- 1992
-
In: International Journal of Supercomputer Applications. ; 6:3, s. 241-256
-
Journal article (peer-reviewed)abstract
- An all-to-all broadcast algorithm that exploits concur rent communication on all channels of the Connection Machine system CM-200 binary cube network is de scribed. Issues in integrating a physical all-to-all broad cast between processing nodes into a language envi ronment using a global address space are discussed. Timings for the physical broadcast between nodes and for the virtual broadcast are given. The peak data transfer rate for the physical broadcast on a CM-200 is 5.9 gigabytes/sec, and the peak rate for the virtual broadcast is 31 gigabytes/sec. Array reshaping is an effective performance optimization technique. An ex ample is given where reshaping improved perfor mance by a factor of 7 by reducing the amount of local data motion. We also show how to exploit symmetry for computation of an interaction matrix using the all- to-all broadcast function. Further optimizations are suggested for N-body-type calculations. Using the all- to-all broadcast function, a peak rate of 9.3 GFLOPS/ sec has been achieved for the N-body computations in 32-bit precision on a 2,048 node Connection Machine system CM-200.
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| 20. |
- Chiang, Chao-Lin, et al.
(author)
-
Residue Arithmetic and VLSI
- 1983
-
Conference paper (peer-reviewed)abstract
- In the residue number system arithmetic is carried out on each digit individually. There is no carry chain. This locality is of particular interest in VLSI. An evaluation of different implementations of residue arithmetic is carried out, and the effects of reduced feature sizes estimated. At the current state of technology the traditional table lookup method is preferable for a range that requires a maximum modulus that is represented by up to 4 bits, while an array of adders offers the best performance fur 7 or more bits. A combination of adders and tables covers 5 and 6 bits the best. At 0.5 mu m feature size table lookup is competitive only up to 3 bits, These conclusions are based on sample designs in nMOS.
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| 21. |
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| 22. |
- Cohen, D, et al.
(author)
-
Mathematical Approach to Computational Networks
- 1983
-
Conference paper (peer-reviewed)abstract
- This report deals with design principles for iterative computational networks. Such computational networks are used for performing repetitive computations which typically are not data-dependent. Most of the signal processing algorithms, like FFT and filtering, belong to this class. The main idea in this report is the development of mathematical notation for expressing such designs. This notation captures the important features and properties of these computational networks, and can be used for analyzing, designing, and objectively evaluating computational networks.
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| 23. |
- Cooper, K., et al.
(author)
-
New Grid Scheduling and Rescheduling Methods in the GrADS Project
- 2004
-
Conference paper (peer-reviewed)abstract
- Summary form only given. The goal of the Grid Application Development Software (GrADS) project is to provide programming tools and an execution environment to ease program development for the grid. We present recent extensions to the GrADS software framework: 1. A new approach to scheduling workflow computations, applied to a 3D image reconstruction application; 2. A simple stop/migrate/restart approach to rescheduling grid applications, applied to a QR 3. A process-swapping approach to rescheduling, applied to an N-body simulation. Experiments validating these methods were carried out on both the GrADS MacroGrid (a small but functional grid) and the MicroGrid (a controlled emulation of the grid) and the results were demonstrated at the SC2003 conference.
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| 24. |
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| 25. |
- Djane, N K, et al.
(author)
-
Chromium speciation in natural waters using serially connected supported liquid membranes.
- 1999
-
In: Talanta. - 1873-3573. ; 48:5, s. 1121-1132
-
Journal article (peer-reviewed)abstract
- A supported liquid membrane (SLM) method for the speciation of chromium has been developed. The method is based on selective extraction and enrichment of anionic Cr(VI) and cationic Cr(III) species in two serially connected SLM units. Methyltricaprylammonium chloride (Aliquat) and di-(2-ethylhexyl) phosphoric acid (DEHPA), respectively were used as the selective extractants in the membrane liquid. Graphite furnace atomic absorption spectrometry (GFAAS) was utilised for final determination. Optimised conditions for the DEHPA membrane were, sample solution at pH 3, acceptor solution 0.1 M HNO(3) and 10% w/w carrier in kerosene. The corresponding values for the Aliquat membrane were pH 7, 0.75 M HNO(3) and 6% w/w carrier in di-n-hexylether. This gave extraction efficiencies for Cr(III) and Cr(VI) of 90 and 40%, respectively. The method was used to measure the concentration of Cr III and Cr VI in surface water from an abandoned tannery site. Storage experiments at different pH showed that preservation at neutral pH gave almost constant values over a period of one month. At acidic pH (pH=3.0) the concentration of Cr(VI) decreased rapidly while the concentration of Cr(III) increased. The detection limit, expressed as three times the standard deviation of enriched blank samples was 0.01 mug l(-1).
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| 26. |
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| 27. |
- Edelman, Alan, et al.
(author)
-
Index Transformation Algorithms in a Linear Algebra Framework
- 1994
-
In: IEEE Transactions on Parallel and Distributed Systems. - : Institute of Electrical and Electronics Engineers (IEEE). - 1045-9219 .- 1558-2183. ; 5:12, s. 1302-1309
-
Journal article (peer-reviewed)abstract
- We present a linear algebraic formulation for a class of index transformations such as Gray code encoding and decoding, matrix transpose, bit reversal, vector reversal, shuffles, and other index or dimension permutations. This formulation unifies, simplifies, and can be used to derive algorithms for hypercube multiprocessors. We show how all the widely known properties of Gray codes, and some not so well-known properties as well, can be derived using this framework. Using this framework, we relate hypercube communications algorithms to Gauss-Jordan elimination on a matrix of 0's and 1's.
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| 28. |
- Engquist, Björn, et al.
(author)
-
Proceedings PDC Seventh Annual Conference : Simulation and Visualization on the Grid
- 2000. - 13
-
Book (peer-reviewed)abstract
- The Grid is an emerging computational infrastructure, similar to the pervasive energy infrastructure provided by national power grids. Simulation and Visualization on the Grid focuses on applications and technologies on this emerging computational Grid. Readers will find interesting discussions of such Grid technologies as distributed file I/O, clustering, CORBA software infrastructure, tele-immersion, interaction environments, visualization steering and virtual reality as well as applications in biology, chemistry and physics. A lively panel discussion addresses current successes and pitfalls of the Grid. This book provides an understanding of the Grid that offers a persistent, wide-scale infrastructure for solving problems.
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| 29. |
- Feig, Michael, et al.
(author)
-
Large Scale Data Repository : Design of a Molecular Dynamics Trajectory Database
- 1999
-
In: Future generations computer systems. - : Elsevier. - 0167-739X .- 1872-7115. ; 16:1, s. 101-110
-
Journal article (peer-reviewed)abstract
- The design of a molecular dynamics trajectory database is presented as an example of the organization of large-scale dynamic distributed repositories for scientific data. Large scientific datasets are usually interpreted through reduced data calculated by analysis functions. This allows a database architecture in which the analyzed datasets, that are kept in addition to the raw datasets, are transferred to a database user. A flexible user interface with a well defined Application Program Interface (API) allows for a wide array of analysis functions and the incorporation of user defined functions is a critical part of the database design. An analysis function is executed only when the requested analysis result is not available from an earlier request. A prototype implementation used to gain initial practical experiences with performance and scalability is presented.
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| 30. |
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| 31. |
- Gardfjäll, Peter, 1979-, et al.
(author)
-
Scalable Grid-wide capacity allocation with the SweGrid Accounting System (SGAS)
- 2008
-
In: Concurrency and Computation. - : Wiley. - 1532-0626 .- 1532-0634. ; 20:18, s. 2089-2122
-
Journal article (peer-reviewed)abstract
- The SweGrid Accounting System (SGAS) allocates capacity in collaborative Grid environments by coordinating enforcement of Grid-wide usage limits as a means to offer usage guarantees and prevent overuse. SGAS employs a credit-based allocation model where Grid capacity is granted to projects via Grid-wide quota allowances that can be spent across the Grid resources. The resources Collectively enforce these allowances in a soft, real-time manner. SGAS is built on service-oriented principles with a strong focus on interoperability, and Web services standards. This article covers the SGAS design and implementation, which, besides addressing inherent Grid challenges (scale, security, heterogeneity, decentralization), emphasizes generality and flexibility to produce a customizable system with lightweight integration into different middleware and scheduling system combinations. We focus the discussion around the system design, a flexible allocation model, middleware integration experiences and scalability improvements via a distributed virtual banking system, and finally, an extensive set of testhed experiments. The experiments evaluate the performance of SGAS in terms of response times, request throughput, overall system scalability, and its performance impact on the Globus Toolkit 4 job submission software. We conclude that, for all practical purposes, the quota enforcement overhead incurred by SGAS on job submissions is not a limiting factor for the job-handling capacity of the job submission software.
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| 32. |
- George, William, et al.
(author)
-
POLYSHIFT Communications Software for the Connection Machine System CM–200
- 1994
-
In: Scientific Programming. - 1058-9244 .- 1875-919X. ; 3:1, s. 83-99
-
Journal article (peer-reviewed)abstract
- We describe the use and implementation of a polyshift function PSHIFT for circular shifts and end-offs shifts. Polyshift is useful in many scientific codes using regular grids, such as finite difference codes in several dimensions, and multigrid codes, molecular dynamics computations, and in lattice gauge physics computations, such as quantum chromodynamics (QCD) calculations. Our implementation of the PSHIFT function on the Connection Machine systems CM-2 and CM-200 offers a speedup of up to a factor of 3-4 compared with CSHIFT when the local data motion within a node is small. The PSHIFT routine is included in the Connection Machine Scientific Software Library (CMSSL).
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| 33. |
- Gerogiannis, D.C, et al.
(author)
-
Histogram Computation on Distributed Memory Architectures
- 1989
-
In: Concurrency: Practice and Experience. - : Wiley. - 1040-3108 .- 1096-9128. ; 1:2, s. 219-237
-
Journal article (peer-reviewed)abstract
- One data-independent and one data-dependent algorithm for the computation of image histograms on parallel computers are presented, analysed and implemented on the Connection Machine system CM-2. The data-dependent algorithm has a lower requirement on communication bandwidth by only transferring bins with a non-zero count. Both algorithms perform all-to-all reduction, which is implemented through a sequence of exchanges as defined by a butterfly network. The two algorithms are compared based on predicted and actual performance on the Connection Machine CM-2. With few pixels per processor the data-dependent algorithm requires in the order of √B data transfers for B bins compared to B data transfers for the data-independent algorithm. As the number of pixels per processor grows the advantage of the data-dependent algorithm decreases. The advantage of the data-dependent algorithm increases with the number of bins of the histogram.
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| 34. |
- Gulevski, Stephanie, et al.
(author)
-
MRI morphological characteristics of lymph nodes in anal squamous cell carcinoma
- 2024
-
In: Abdominal Radiology. - 2366-004X. ; 49:4, s. 1042-1050
-
Journal article (peer-reviewed)abstract
- ObjectivesPre-treatment staging of anal squamous cell carcinoma (ASCC) includes pelvic MRI and [18F]-fluorodeoxyglucose positron emission tomography with computed tomography (PET-CT). MRI criteria to define lymph node metastases (LNMs) in ASCC are currently lacking. The aim of this study was to describe the morphological characteristics of lymph nodes (LNs) on MRI in ASCC patients with PET-CT-positive LNs.MethodsASCC patients treated at Skåne University Hospital between 2009 and 2017 were eligible for inclusion if at least one positive LN according to PET-CT and a pre-treatment MRI were present. All PET-CT-positive LNs and PET-CT-negative LNs were retrospectively identified on baseline MRI. Each LN was independently classified according to pre-determined morphological characteristics by two radiologists blinded to clinical patient information.ResultsSixty-seven ASCC patients were included, with a total of 181 PET-CT-positive LNs identified on baseline MRI with a median short-axis diameter of 9.0 mm (range 7.5–12 mm). MRI morphological characteristics of PET-CT-positive LNs included regular contour (87%), round shape (89%), and homogeneous signal intensity on T2-weighed images (67%). An additional 78 PET-CT-negative LNs were identified on MRI. These 78 LNs had a median size of 6.8 mm (range 5.5–8.0 mm). The majority of PET-CT-negative LNs had a regular contour, round shape, and a homogeneous signal that was congruent to the primary tumor.ConclusionsThere are MRI-specific morphological characteristics for pelvic LNs in ASCC. PET-CT-positive and negative LNs share similar morphological features apart from size, with PET-CT-positive LNs being significantly larger. Further studies are needed to determine discrimination criteria for LNM in ASCC.
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| 35. |
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| 36. |
- Harris, Tim, et al.
(author)
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Matrix Multiplication on the Connection Machine
- 1989
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Conference paper (peer-reviewed)abstract
- A data parallel implementation of the multiplication of matrices of arbitrary shapes and sizes is presented. A systolic algorithm based on a rectangular processor layout is used by the implementation. All processors contain submatrices of the same size for a given operand. Matrix-vector multiplication is used as a primitive for local matrix-matrix multiplication in the Connection Machine system CM-2 implementation. The peak performance of the local matrix-matrix multiplication is in excess of 20 Gflops s-1. The overall algorithm including all required data motion has a peak performance of 5.8 Gflops s-1.
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| 37. |
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| 38. |
- Ho, Ching-Tien, et al.
(author)
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Algorithms for Matrix Transposition on Boolean Cube Configured Ensemble Architectures
- 1987
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Conference paper (peer-reviewed)abstract
- In a multiprocessor with distributed storage the data structures have a significant impact on the communication complexity. In this paper we present a few algorithms for performing matrix transposition on a Boolean $n$-cube. One algorithm performs the transpose in a time proportional to the lower bound both with respect to communication start-ups and to element transfer times. We present algorithms for transposing a matrix embedded in the cube by a binary encoding, a binary-reflected Gray code encoding of rows and columns, or combinations of these two encodings. The transposition of a matrix when several matrix elements are identified to a node by consecutive or cyclic partitioning is also considered and lower bound algorithms given. Experimental data are provided for the Intel iPSC and the Connection Machine.
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| 39. |
- Ho, Ching-Tien, et al.
(author)
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An Efficient Algorithm for Gray–to–Binary Permutation on Hypercubes
- 1994
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In: Journal of Parallel and Distributed Computing. - 0743-7315 .- 1096-0848. ; 20:1, s. 114-120
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Journal article (peer-reviewed)abstract
- Both Gray code and binary code are frequently used in mapping arrays into hypercube architectures. While the former is preferred when communication between adjacent array elements is needed, the latter is preferred for FFT-type communication. When different phases of computations have different types of communication patterns, the need arises to remap the data. We give a nearly optimal algorithm for permuting data from a Gray code mapping to a binary code mapping on a hypercube with communication restricted to one input and one output channel per node at a time. Our algorithm improves over the best previously known algorithm [6] by nearly a factor of two and is optimal to within a factor of n=(n Gamma 1) with respect to data transfer time on an n-cube. The expected speedup is confirmed by measurements on an Intel iPSC/2 hypercube
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| 40. |
- Ho, Cieng-Tien, et al.
(author)
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Dilation d Embeddings of a Hyper–Pyramid into a Hypercube
- 1989
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Conference paper (peer-reviewed)abstract
- A P(k, d) hyper-pyramid is a level structure of k Boolean cubes where the cube at level i is of dimension id, and a node at level i - 1 connects to every node in a d dimensional Boolean subcube at level i, except for the leaf level k. Hyper-pyramids contain pyramids as proper subgraphs. We show that a P(k, d) hyper-pyramid can be embedded in a Boolean cube with minimal expansion and dilation d. The congestion is bounded from above by 2d+1/d+2 and from below by 1 + 2d-d/kd+1. For P(k, 2) hyper-pyramids we present a dilation 2 and congestion 2 embedding. As a corollary a complete n-ary tree can be embedded in a Boolean cube with dilation max(2, log2n) and expansion 2klog2n + 1/nk+1-1/n-1. We also discuss multiple pyramid embeddings.
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| 41. |
- Ho, Ching-Tien, et al.
(author)
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Distributed Routing Algorithms for Broadcasting and Personalized Communication in Hypercubes
- 1986
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Conference paper (peer-reviewed)abstract
- High communication bandwidth in standard technologies is more expensive to realize than a high rate of arithmetic or logic operations. The effective utilization of communication resources is crucial for good overall performance in highly concurrent systems. In this paper we address two different communication problems in Boolean n-cube configured multiprocessors: 1) broadcasting, i.e., distribution of common data from a single source to all other nodes, and 2) sending personalized data from a single source to all other nodes. The well known spanning tree algorithm obtained by bit-wise complementation of leading zeroes (referredto as the SBT algorithm for Spanning Binomial nee) is compared with an algorithm using multiple spanning binomial trees (MSBT). The MSBT dgorithm offers a potential speed-up over the SBT dgorithm by afactor of log2 N. We also present a balanced #panning tree algorithm (BST) that offers a lower complexity than the SBT algorithm for Case 2. The potential improvement is by a factor of 3 log2 N. The analysis takes into account the size of the data sets, the communication bandwidth, and the overhead in communication. We also provide some experimental data for the Intel iPSC'd7.
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| 42. |
- Ho, Ching-Tien, et al.
(author)
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Embedding Hyper–pyramids in Hypercubes
- 1994
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In: IBM Journal of Research and Development. - : IBM. - 0018-8646 .- 2151-8556. ; 38:1, s. 31-45
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Journal article (peer-reviewed)
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| 43. |
- Ho, Ching-Tien, et al.
(author)
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Embedding Meshes in Boolean Cubes by Graph Decomposition
- 1990
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In: Parallel Computing. - : Elsevier BV. - 0167-8191 .- 1872-7336. ; 8:4, s. 325-339
-
Journal article (peer-reviewed)abstract
- This paper explores the embeddings of multidimensional meshes into minimal Boolean cubes by graph decomposition. The dilation and the congestion of the product graph (G1 × G2) → (H1 × H2) is the maximum of the dilation and congestion for the two embeddings G1 → H1 and G2 → H2. The graph decomposition technique can be used to improve the average dilation and average congestion. The graph decomposition technique combined with some particular two-dimensional embeddings allows for minimal-expansion, dilation-two, congestion-two embeddings of about 87% of all two-dimensional meshes, with a significantly lower average dilation and congestion than by modified line compression. For three-dimensional meshes we show that the graph decomposition technique, together with two three-dimensional mesh embeddings presented in this paper and modified line compression, yields dilation-two embeddings of more than 96% of all three-dimensional meshes contained in a 512 × 512 × 512 mesh. The graph decomposition technique is also used to generalize the embeddings to meshes with wrap-around. The dilation increases by at most one compared to a mesh without wraparound. The expansion is preserved for the majority of meshes, if a wraparound feature is added to the mesh.
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| 44. |
- Ho, Ching-Tien, et al.
(author)
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Embedding Meshes into Small Boolean Cubes
- 1990
-
Conference paper (peer-reviewed)abstract
- The embedding of arrays in Boolean cubes, when there are more array elements than nodes in the cube, can always be made with optimal load-factor by reshaping the array to a one-dimensional array. We show that the dilation for such an embedding is of an .to x .t1 x - + x &-I array in an n-cube.Dila tion one embeddings can be obtained by splitting each axis into segments and assigning segments to nodes in the cube by a Gray code. The load-factor is optimal if the axis lengths contain sufficiently many powers of two. The congestion is minimized, if the segment lengths along the different axes are as equal as possible, for the cube configured with at most as many axes as the array. A further decrease in the congestion is possible if the array is partitioned into subarrays, and corresponding axis of different subarrays make use of edge-disjoint Hamiltonian cycles within subcubes. The congestion can also be reduced by using multiple paths between pairs of cube nodes, i.e., by using “fat” edges.
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| 45. |
- Ho, Ching-Tien, et al.
(author)
-
Embedding Three–Dimensional Meshes in Boolean Cubes by Graph Decomposition
- 1990
-
Conference paper (peer-reviewed)abstract
- This paper explores the embeddings of multidimensional meshes into minimal Boolean cubes by graph decomposition. The graph decomposition technique can be used to improve the average dilation and average congestion. The graph decomposition technique combined with some particular two-dimensional embeddings allows for minimal-expansion, dilation-two, congestion-two embeddings of about 87% of all two-dimensional meshes, with a significantly lower average dilation and congestion than by modified line compression. For three-dimensional meshes the authors show that the graph decomposition technique, together with two three-dimensional mesh embeddings presented in this paper and modified line compression, yields dilation-two embeddings of more than 96% of all three dimensional meshes contained in a 512 {times} 512 {times} 512 mesh.
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| 46. |
- Ho, Ching-Tien, et al.
(author)
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Matrix Multiplication on Hypercubes Using Full Bandwidth and Constant Storage
- 1991
-
Conference paper (peer-reviewed)abstract
- For matrix multiplication on hypercube multiproces- sors with the product matrix accumulated in place a processor must receive about P2= p N elements of each input operand, with operands of size P P distributed evenly over N processors. With concurrent communi- cation on all ports, the number of element transfers in sequence can be reduced to P2= p N logN for each input operand. We present a two-level partitioning of the matrices and an algorithm for the matrix multipli- cation with optimal data motion and constant storage. The algorithm has sequential arithmetic complexity 2P3, and parallel arithmetic complexity 2P 3=N. The algorithm has been implemented on the Connection Machine model CM-2. For the performance on the 8K CM-2, we measured about 1.6 G ops, which would scale up to about 13 G ops for a 64K full machine.
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| 47. |
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| 48. |
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| 49. |
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| 50. |
- Ho, Ching-Tien, et al.
(author)
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Optimizing Tridiagonal Solvers for the Alternating Direction Method on Boolean Cube Multiprocessors
- 1990
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In: SIAM Journal on Scientific Computing. - : Society for Industrial & Applied Mathematics (SIAM). - 1064-8275 .- 1095-7197. ; 11:3, s. 563-592
-
Journal article (peer-reviewed)abstract
- Sets of tridiagonal systems occur in many applications. Fast Poisson solvers and Alternate Direction Methods make use of tridiagonal system solvers. Network-based multiprocessors provide a cost-effective alternative to traditional supercomputer architectures. The complexity of concurrent algorithms for the solution of multiple tridiagonal systems on Boolean-cube-configured multiprocessors with distributed memory are investigated. Variations of odd-even cyclic reduction, parallel cyclic reduction, and algorithms making use of data transposition with or without substructuring and local elimination, or pipelined elimination, are considered. A simple performance model is used for algorithm comparison, and the validity of the model is verified on an Intel iPSC/ 1. For many combinations of machine and system parameters, pipelined elimination, or equation transposition with or without substructuring is optimum. Hybrid algorithms that at any stage choose the best algorithm among the considered ones for the remainder of the problem are presented. It is shown that the optimum partitioning of a set of independent tridiagonal systems among a set of processors yields the embarrassingly parallel case. If the systems originate from a lattice and solutions are computed in alternating directions, then to first order the aspect ratio of a computational lattice shall be the same as that of the lattice forming the base for the equations. The experiments presented here demonstrate the importance of combining in the communication system for architectures with a relatively high communications start-up time.
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