86 research outputs found
Towards as assessment of fault-tolerant design principles for software
Several topics related to the assessment of fault-tolerant design principles for software are presented in outline form. A coincident errors model, discrete intensity distribution and the effects of coincident errors are discussed
Fault-tolerant software experiment objectives and status
Software redundancy is discussed in general terms in outline form. Background, observations, major issues, experiment objectives and the current status of the project are noted
Preliminary design of the redundant software experiment
The goal of the present experiment is to characterize the fault distributions of highly reliable software replicates, constructed using techniques and environments which are similar to those used in comtemporary industrial software facilities. The fault distributions and their effect on the reliability of fault tolerant configurations of the software will be determined through extensive life testing of the replicates against carefully constructed randomly generated test data. Each detected error will be carefully analyzed to provide insight in to their nature and cause. A direct objective is to develop techniques for reducing the intensity of coincident errors, thus increasing the reliability gain which can be achieved with fault tolerance. Data on the reliability gains realized, and the cost of the fault tolerant configurations can be used to design a companion experiment to determine the cost effectiveness of the fault tolerant strategy. Finally, the data and analysis produced by this experiment will be valuable to the software engineering community as a whole because it will provide a useful insight into the nature and cause of hard to find, subtle faults which escape standard software engineering validation techniques and thus persist far into the software life cycle
An experimental evaluation of software redundancy as a strategy for improving reliability
The strategy of using multiple versions of independently developed software as a means to tolerate residual software design faults is suggested by the success of hardware redundancy for tolerating hardware failures. Although, as generally accepted, the independence of hardware failures resulting from physical wearout can lead to substantial increases in reliability for redundant hardware structures, a similar conclusion is not immediate for software. The degree to which design faults are manifested as independent failures determines the effectiveness of redundancy as a method for improving software reliability. Interest in multi-version software centers on whether it provides an adequate measure of increased reliability to warrant its use in critical applications. The effectiveness of multi-version software is studied by comparing estimates of the failure probabilities of these systems with the failure probabilities of single versions. The estimates are obtained under a model of dependent failures and compared with estimates obtained when failures are assumed to be independent. The experimental results are based on twenty versions of an aerospace application developed and certified by sixty programmers from four universities. Descriptions of the application, development and certification processes, and operational evaluation are given together with an analysis of the twenty versions
Open environments to support systems engineering tool integration: A study using the Portable Common Tool Environment (PCTE)
A study of computer engineering tool integration using the Portable Common Tool Environment (PCTE) Public Interface Standard is presented. Over a 10-week time frame, three existing software products were encapsulated to work in the Emeraude environment, an implementation of the PCTE version 1.5 standard. The software products used were a computer-aided software engineering (CASE) design tool, a software reuse tool, and a computer architecture design and analysis tool. The tool set was then demonstrated to work in a coordinated design process in the Emeraude environment. The project and the features of PCTE used are described, experience with the use of Emeraude environment over the project time frame is summarized, and several related areas for future research are summarized
Flight Demonstration of Integrated Airport Surface Technologies for Increased Capacity and Safety
A flight demonstration was conducted to address airport surface movement area capacity and safety issues by providing pilots with enhanced situational awareness information. The demonstration presented an integration of several technologies to government and industry representatives. These technologies consisted of an electronic moving map display in the cockpit, a Differential Global Positioning system (DGPS) receiver, a high speed very high frequency (VHF) data link, an Airport Surface Detection Equipment (ASDE-3) radar, and the Airport Movement Area Safety System (AMASS). Aircraft identification was presented to an air traffic controller on an AMASS display. The onboard electronic map included the display of taxi routes, hold instructions, and clearances, which were sent to the aircraft via data link by the controller. The map also displayed the positions of other traffic and warning information, which were sent to the aircraft automatically from the ASDE-3/AMASS system. This paper describes the flight demonstration in detail, along with test results
All-sky search for long-duration gravitational-wave bursts in the third Advanced LIGO and Advanced Virgo run
After the detection of gravitational waves from compact binary coalescences, the search for transient gravitational-wave signals with less well-defined waveforms for which matched filtering is not well suited is one of the frontiers for gravitational-wave astronomy. Broadly classified into âshortâ âČ1ââs and âlongâ âł1ââs duration signals, these signals are expected from a variety of astrophysical processes, including non-axisymmetric deformations in magnetars or eccentric binary black hole coalescences. In this work, we present a search for long-duration gravitational-wave transients from Advanced LIGO and Advanced Virgoâs third observing run from April 2019 to March 2020. For this search, we use minimal assumptions for the sky location, event time, waveform morphology, and duration of the source. The search covers the range of 2â500 s in duration and a frequency band of 24â2048 Hz. We find no significant triggers within this parameter space; we report sensitivity limits on the signal strength of gravitational waves characterized by the root-sum-square amplitude hrss as a function of waveform morphology. These hrss limits improve upon the results from the second observing run by an average factor of 1.8
Constraints on dark photon dark matter using data from LIGO's and Virgo's third observing run
We present a search for dark photon dark matter that could couple to
gravitational-wave interferometers using data from Advanced LIGO and Virgo's
third observing run. To perform this analysis, we use two methods, one based on
cross-correlation of the strain channels in the two nearly aligned LIGO
detectors, and one that looks for excess power in the strain channels of the
LIGO and Virgo detectors. The excess power method optimizes the Fourier
Transform coherence time as a function of frequency, to account for the
expected signal width due to Doppler modulations. We do not find any evidence
of dark photon dark matter with a mass between eV/, which corresponds to frequencies between 10-2000
Hz, and therefore provide upper limits on the square of the minimum coupling of
dark photons to baryons, i.e. dark matter. For the
cross-correlation method, the best median constraint on the squared coupling is
at eV/; for the
other analysis, the best constraint is at eV/. These limits improve upon those obtained
in direct dark matter detection experiments by a factor of for
eV/, and are, in absolute terms, the
most stringent constraint so far in a large mass range eV/.Comment: 20 pages, 7 figure
Search for continuous gravitational wave emission from the Milky Way center in O3 LIGO--Virgo data
We present a directed search for continuous gravitational wave (CW) signals
emitted by spinning neutron stars located in the inner parsecs of the Galactic
Center (GC). Compelling evidence for the presence of a numerous population of
neutron stars has been reported in the literature, turning this region into a
very interesting place to look for CWs. In this search, data from the full O3
LIGO--Virgo run in the detector frequency band have been
used. No significant detection was found and 95 confidence level upper
limits on the signal strain amplitude were computed, over the full search band,
with the deepest limit of about at .
These results are significantly more constraining than those reported in
previous searches. We use these limits to put constraints on the fiducial
neutron star ellipticity and r-mode amplitude. These limits can be also
translated into constraints in the black hole mass -- boson mass plane for a
hypothetical population of boson clouds around spinning black holes located in
the GC.Comment: 25 pages, 5 figure
GWTC-3:compact binary coalescences observed by LIGO and Virgo during the second part of the third observing run
The third Gravitational-Wave Transient Catalog (GWTC-3) describes signals detected with Advanced LIGO and Advanced Virgo up to the end of their third observing run. Updating the previous GWTC-2.1, we present candidate gravitational waves from compact binary coalescences during the second half of the third observing run (O3b) between 1 November 2019, 15â¶00 Coordinated Universal Time (UTC) and 27 March 2020, 17â¶00 UTC. There are 35 compact binary coalescence candidates identified by at least one of our search algorithms with a probability of astrophysical origin astro>0.5. Of these, 18 were previously reported as low-latency public alerts, and 17 are reported here for the first time. Based upon estimates for the component masses, our O3b candidates with astro>0.5 are consistent with gravitational-wave signals from binary black holes or neutron-starâblack-hole binaries, and we identify none from binary neutron stars. However, from the gravitational-wave data alone, we are not able to measure matter effects that distinguish whether the binary components are neutron stars or black holes. The range of inferred component masses is similar to that found with previous catalogs, but the O3b candidates include the first confident observations of neutron-starâblack-hole binaries. Including the 35 candidates from O3b in addition to those from GWTC-2.1, GWTC-3 contains 90 candidates found by our analysis with astro>0.5 across the first three observing runs. These observations of compact binary coalescences present an unprecedented view of the properties of black holes and neutron stars
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