8,200 research outputs found
Towards compliant distributed shared memory
Copyright © 2002 IEEEThere exists a wide spectrum of coherency models for use in distributed shared memory (DSM) systems. The choice of model for an application should ideally be based on the application's data access patterns and phase changes. However, in current systems, most, if not all of the parameters of the coherency model are fixed in the underlying DSM system. This forces the application either to structure its computations to suit the underlying model or to endure an inefficient coherency model. This paper introduces a unique approach to the provision of DSM based on the idea of compliance. Compliance allows an application to specify how the system should most effectively operate through a separation between mechanism, provided by the underlying system, and policy, pro-vided by the application. This is in direct contrast with the traditional view that an application must mold itself to the hard-wired choices that its operating platform has made. The contribution of this work is the definition and implementation of an architecture for compliant distributed coherency management. The efficacy of this architecture is illustrated through a worked example.Falkner, K. E.; Detmold, H.; Munro, D. S.; Olds, T
Using khazana to support distributed application development
technical reportOne of the most important services required by most distributed applications is some form of shared data management, e.g., a directory service manages shared directory entries while groupware manages shared documents. Each such application currently must implement its own data management mechanisms, because existing runtime systems are not flexible enough to support all distributed applications efficiently. For example, groupware can be efficiently supported by a distributed object system, while a distributed database would prefer a more low-level storage abstraction. The goal of Khazana is to provide programmer's with configurable components that support the data management services required by a wide variety of distributed applications, including: consistent caching, automated replication and migration of data, persistence, access control, and fault tolerance. It does so via a carefully designed set of interfaces that supports a hierarchy of data abstractions, ranging from flat data to C++/Java objects, and that give programmers a great of control over how their data is managed. To demonstrate the effectiveness of our design, we report on our experience porting three applications to Khazana: a distributed file system, a distributed directory service, and a shared whiteboard
Khazana An infrastructure for building distributed services
technical reportEssentially all distributed systems?? applications?? and services at some level boil down to the problem of man aging distributed shared state Unfortunately?? while the problem of managing distributed shared state is shared by many applications?? there is no common means of managing the data every application devises its own solution We have developed Khazana?? a distributed service exporting the abstraction of a distributed per sistent globally shared store that applications can use to store their shared state Khazana is responsible for performing many of the common operations needed by distributed applications?? including replication?? consis tency management?? fault recovery?? access control?? and location management Using Khazana as a form of middleware?? distributed applications can be quickly de veloped from corresponding uniprocessor applications through the insertion of Khazana data access and syn chronization operation
Khazana an infrastructure for building distributed services
technical reportEssentially all distributed systems, applications and service at some level boil down to the problem of managing distributed shared state. Unfortunately, while the problem of managing distributed shared state is shared by man applications, there is no common means of managing the data - every application devises its own solution. We have developed Khazana, a distributed service exporting the abstraction of a distributed persistent globally hared store that applications can use to store their shared state. Khazana is responsible for performing many of the common operations needed by distributed applications, including replication, consistency management, fault recovery, access control, and location management. Using Khazana as a form of middleware, distributed applications can be quickly developed from corresponding uniprocessor applications through the insertion of Khazana data access and synchronization operations
Quiet but still bright: XMM-Newton observations of the soft gamma-ray repeater SGR 0526-66
SGR 0526-66 was the first soft gamma-ray repeater (SGR) from which a giant
flare was detected in March 1979, suggesting the existence of magnetars, i.e.
neutron stars powered by the decay of their extremely strong magnetic field.
Since then, very little information has been obtained on this object, mainly
because it has been burst-inactive since 1983 and the study of its persistent
X-ray emission has been hampered by its large distance and its location in a
X-ray bright supernova remnant in the Large Magellanic Cloud. Here we report on
a comprehensive analysis of all the available XMM-Newton observations of SGR
0526-66. In particular, thanks to a deep observation taken in 2007, we measured
its pulsation period (P = 8.0544 +/- 0.0002 s) 6 years after its latest
detection by Chandra. This allowed us to detect for the first time a
significant reduction of its spin-down rate. From a comparison with two shorter
XMM-Newton observations performed in 2000 and 2001, we found no significant
changes in the spectrum, which is well modelled by an absorbed power-law with
nH = 4.6E+21 cm^-2 and photon index = 3.27. The high luminosity (about 4E+35
erg/s, in the 1-10 keV energy band) still observed about 25 years after the
latest detection of bursting activity places SGR 0526-66 in the group of bright
and persistent magnetar candidates.Comment: 5 pages, 3 figures (1 color) and 2 tables; Accepted for publication
in MNRAS Letter
The Wide-Field X and Gamma-Ray Telescope ECLAIRs aboard the Gamma-Ray Burst Multi-Wavelength Space Mission SVOM
The X and Gamma-ray telescope ECLAIRs is foreseen to be launched on a low
Earth orbit (h=630 km, i=30 degrees) aboard the SVOM satellite (Space-based
multi-band astronomical Variable Objects Monitor), a French-Chinese mission
with Italian contribution. Observations are expected to start in 2013. It has
been designed to detect and localize Gamma-Ray Bursts (GRBs) or persistent
sources of the sky, thanks to its wide field of view (about 2 sr) and its
remarkable sensitivity in the 4-250 keV energy range, with enhanced imaging
sensitivity in the 4-70 keV energy band. These characteristics are well suited
to detect highly redshifted GRBs, and consequently to provide fast and accurate
triggers to other onboard or ground-based instruments able to follow-up the
detected events in a very short time from the optical wavelength bands up to
the few MeV Gamma-Ray domain.Comment: Proccedings of the "2008 Nanjing GRB Conference", June 23-27 2008,
Nanjing, Chin
Approximating A Dsmâ5 Diagnosis Of Ptsd Using DsmâIv Criteria
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/111929/1/da22364.pd
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