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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Making reliable distributed systems in the presence of software errors

Armstrong, Joe January 2003 (has links)
The work described in this thesis is the result of aresearch program started in 1981 to find better ways ofprogramming Telecom applications. These applications are largeprograms which despite careful testing will probably containmany errors when the program is put into service. We assumethat such programs do contain errors, and investigate methodsfor building reliable systems despite such errors. The research has resulted in the development of a newprogramming language (called Erlang), together with a designmethodology, and set of libraries for building robust systems(called OTP). At the time of writing the technology describedhere is used in a number of major Ericsson, and Nortelproducts. A number of small companies have also been formedwhich exploit the technology. The central problem addressed by this thesis is the problemof constructing reliablesystems from programs which maythemselves contain errors. Constructing such systems imposes anumber of requirements on any programming language that is tobe used for the construction. I discuss these languagerequirements, and show how they are satisfied by Erlang. Problems can be solved in a programming language, or in thestandard libraries which accompany the language. I argue howcertain of the requirements necessary to build a fault-tolerantsystem are solved in the language, and others are solved in thestandard libraries. Together these form a basis for buildingfault-tolerant software systems. No theory is complete without proof that the ideas work inpractice. To demonstrate that these ideas work in practice Ipresent a number of case studies of large commerciallysuccessful products which use this technology. At the time ofwriting the largest of these projects is a major Ericssonproduct, having over a million lines of Erlang code. Thisproduct (the AXD301) is thought to be one of the most reliableproducts ever made by Ericsson. Finally, I ask if the goal of finding better ways to programTelecom applications was fulfilled --- I also point to areaswhere I think the system could be improved.
2

Making reliable distributed systems in the presence of software errors

Armstrong, Joe January 2003 (has links)
<p>The work described in this thesis is the result of aresearch program started in 1981 to find better ways ofprogramming Telecom applications. These applications are largeprograms which despite careful testing will probably containmany errors when the program is put into service. We assumethat such programs do contain errors, and investigate methodsfor building reliable systems despite such errors.</p><p>The research has resulted in the development of a newprogramming language (called Erlang), together with a designmethodology, and set of libraries for building robust systems(called OTP). At the time of writing the technology describedhere is used in a number of major Ericsson, and Nortelproducts. A number of small companies have also been formedwhich exploit the technology.</p><p>The central problem addressed by this thesis is the problemof constructing reliablesystems from programs which maythemselves contain errors. Constructing such systems imposes anumber of requirements on any programming language that is tobe used for the construction. I discuss these languagerequirements, and show how they are satisfied by Erlang.</p><p>Problems can be solved in a programming language, or in thestandard libraries which accompany the language. I argue howcertain of the requirements necessary to build a fault-tolerantsystem are solved in the language, and others are solved in thestandard libraries. Together these form a basis for buildingfault-tolerant software systems.</p><p>No theory is complete without proof that the ideas work inpractice. To demonstrate that these ideas work in practice Ipresent a number of case studies of large commerciallysuccessful products which use this technology. At the time ofwriting the largest of these projects is a major Ericssonproduct, having over a million lines of Erlang code. Thisproduct (the AXD301) is thought to be one of the most reliableproducts ever made by Ericsson.</p><p>Finally, I ask if the goal of finding better ways to programTelecom applications was fulfilled --- I also point to areaswhere I think the system could be improved.</p>
3

TELEMETRY IN BUNDLES: DELAY-TOLERANT NETWORKING FOR DELAY-CHALLENGED APPLICATIONS

Burleigh, Scott 10 1900 (has links)
International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Delay-tolerant networking (DTN) is a system for constructing automated data networks in which end-to-end communication is reliable despite low data rates, possible sustained interruptions in connectivity, and potentially high signal propagation latency. As such it promises to provide an inexpensive and robust medium for returning telemetry from research vehicles in environments that provide meager support for communications: deep space, the surface of Mars, the poles or the sub- Arctic steppes of Earth, and others. This paper presents an overview of DTN concepts, including “bundles” and the Bundling overlay protocol. One possible scenario for the application of DTN to a telemetry return problem is described, and there is a brief discussion of the current state of DTN technology development.
4

Aspects of advanced controller design and implementation

Arelhi, Roselina January 1999 (has links)
No description available.
5

Using Decline Curve Analysis, Volumetric Analysis, and Bayesian Methodology to Quantify Uncertainty in Shale Gas Reserve Estimates

Gonzalez Jimenez, Raul 1988- 14 March 2013 (has links)
Probabilistic decline curve analysis (PDCA) methods have been developed to quantify uncertainty in production forecasts and reserves estimates. However, the application of PDCA in shale gas reservoirs is relatively new. Limited work has been done on the performance of PDCA methods when the available production data are limited. In addition, PDCA methods have often been coupled with Arp’s equations, which might not be the optimum decline curve analysis model (DCA) to use, as new DCA models for shale reservoirs have been developed. Also, decline curve methods are based on production data only and do not by themselves incorporate other types of information, such as volumetric data. My research objective was to integrate volumetric information with PDCA methods and DCA models to reliably quantify the uncertainty in production forecasts from hydraulically fractured horizontal shale gas wells, regardless of the stage of depletion. In this work, hindcasts of multiple DCA models coupled to different probabilistic methods were performed to determine the reliability of the probabilistic DCA methods. In a hindcast, only a portion of the historical data is matched; predictions are made for the remainder of the historical period and compared to the actual historical production. Most of the DCA models were well calibrated visually when used with an appropriate probabilistic method, regardless of the amount of production data available to match. Volumetric assessments, used as prior information, were incorporated to further enhance the calibration of production forecasts and reserves estimates when using the Markov Chain Monte Carlo (MCMC) as the PDCA method and the logistic growth DCA model. The proposed combination of the MCMC PDCA method, the logistic growth DCA model, and use of volumetric data provides an integrated procedure to reliably quantify the uncertainty in production forecasts and reserves estimates in shale gas reservoirs. Reliable quantification of uncertainty should yield more reliable expected values of reserves estimates, as well as more reliable assessment of upside and downside potential. This can be particularly valuable early in the development of a play, because decisions regarding continued development are based to a large degree on production forecasts and reserves estimates for early wells in the play.
6

En undersøkelse av sammenhengen mellom prinsipper for høyt reliable organisasjoner, teamarbeid og feil i ambulansetjenesten

Pettersen, Rannveig Staal January 2013 (has links)
Det er i dagens helsepolitikk et økende fokus på å styrke pasientsikkerheten i helsetjenesten, og implementering av prinsipper for høyt reliable organisasjoner i disse tjenestene har blitt sett på som et virkemiddel for å redusere pasientskader. Dette er på bakgrunn av at høyt reliable organisasjoner er organisert ut i fra et sikkerhetssystem som gjør de svært gode på å håndtere og forebygge feil og ulykker. Det fokuseres også på viktigheten av gode teamprosesser for å øke sikkerheten i disse tjenestene, samtidig som at teamarbeid blir sett på som et nøkkelprinsipp for høy reliabilitet. Det er likevel lite forskning på sammenhengen mellom teamarbeid, høy reliabilitet og feil, noe som dannet utgangspunktet for denne studien. Det har her blitt testet hvordan et fokus på gode teamprosesser, og prinsipper for høy reliabilitet kan bidra til å redusere feil i ambulansetjenesten, som er en del av spesialisthelsetjenesten i Norge. Resultatene viser at både høy reliabilitet og gode teamprosesser bidrar til å redusere feil, samtidig som det har blitt testet hvordan teamarbeid og høy reliabilitet henger sammen. Gode teamprosesser viser seg å føre til høy reliabilitet, og på denne måten påvirke feil gjennom å fordre reliabel atferd. Ved å teste ulike teamkomponenter opp i mot prinsippene for høy reliabilitet danner studien også et utgangspunkt for hvordan teamtrening kan basere seg på en reliabel oppbygning, og dermed implementeres i tjenesten.
7

Techno-economic analysis of the 100 MW Potchefstroom experimental pebble bed reactor plant / by Yvotte Brits

Brits, Yvotte January 2009 (has links)
Electricity is directly linked to the economy of a country: when electricity is limited and the price for electricity is very high, the high electricity price will have a negative influence on the economy of the country. Owing to the increasing power shortage in the world, and South Africa in particular, today, the need for reliable and economical electricity has risen drastically. The 100 MWth (40 MWe) PEPER power plant is a possible alternative that will help fight the lack of reliable, clean and affordable electricity in the world today. Owing to the small consumption area of the PEPER power plant, each city, mine and industry, for example, can have its own PEPER power plant in order to ensure reliable, affordable and sustainable electricity. This dissertation presents a case study and the relevant economic model for the PEPER power plant in order to determine whether the PEPER power plant may be considered as a possible electricity source. The production costs of the PEPER are presented in US$/kWh and compared with the industrial and household electricity costs (in US$/kWh) of various countries. This is done in order to determine whether it will be economically feasible to construct a First-of-a-kind (FOAK) or Nth-of-a-kind (NOAK) PEPER power plant in the industrial and household sectors of a selected country. In the economic model of the PEPER plant, the fixed capital investment costs for a FOAK PEPER plant were estimated to be US$367,199,411 and the fixed capital investment costs for a NOAK (eighth) PEPER plant were estimated to be US$238,429,665. The working capital for the first two years of the PEPER plant’s lifetime was estimated to be US$17,228,740. The production cost of the PEPER plant was estimated to be 0.038 US$/kWh. The sensitivity analysis conducted demonstrated that FOAK PEPER plants could be established in countries in which the electricity income is 0.145 US$/kWh or more. NOAK PEPER plants (all the PEPER plants constructed after the eighth PEPER Techno-economic analysis of the 100 MWth PEPER plant Confidential 3 plant is erected) could be established in countries with an electricity income of 0.10 US$/kWh or more. The PEPER plant presented here could be used: 1. as a training tool; 2. to test fuels and materials; 3. to accumulate high temperature nuclear data; and 4. as an electricity source for the industrial and household sectors of selected countries. / Thesis (M.Ing. (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2010
8

Techno-economic analysis of the 100 MW Potchefstroom experimental pebble bed reactor plant / by Yvotte Brits

Brits, Yvotte January 2009 (has links)
Electricity is directly linked to the economy of a country: when electricity is limited and the price for electricity is very high, the high electricity price will have a negative influence on the economy of the country. Owing to the increasing power shortage in the world, and South Africa in particular, today, the need for reliable and economical electricity has risen drastically. The 100 MWth (40 MWe) PEPER power plant is a possible alternative that will help fight the lack of reliable, clean and affordable electricity in the world today. Owing to the small consumption area of the PEPER power plant, each city, mine and industry, for example, can have its own PEPER power plant in order to ensure reliable, affordable and sustainable electricity. This dissertation presents a case study and the relevant economic model for the PEPER power plant in order to determine whether the PEPER power plant may be considered as a possible electricity source. The production costs of the PEPER are presented in US$/kWh and compared with the industrial and household electricity costs (in US$/kWh) of various countries. This is done in order to determine whether it will be economically feasible to construct a First-of-a-kind (FOAK) or Nth-of-a-kind (NOAK) PEPER power plant in the industrial and household sectors of a selected country. In the economic model of the PEPER plant, the fixed capital investment costs for a FOAK PEPER plant were estimated to be US$367,199,411 and the fixed capital investment costs for a NOAK (eighth) PEPER plant were estimated to be US$238,429,665. The working capital for the first two years of the PEPER plant’s lifetime was estimated to be US$17,228,740. The production cost of the PEPER plant was estimated to be 0.038 US$/kWh. The sensitivity analysis conducted demonstrated that FOAK PEPER plants could be established in countries in which the electricity income is 0.145 US$/kWh or more. NOAK PEPER plants (all the PEPER plants constructed after the eighth PEPER Techno-economic analysis of the 100 MWth PEPER plant Confidential 3 plant is erected) could be established in countries with an electricity income of 0.10 US$/kWh or more. The PEPER plant presented here could be used: 1. as a training tool; 2. to test fuels and materials; 3. to accumulate high temperature nuclear data; and 4. as an electricity source for the industrial and household sectors of selected countries. / Thesis (M.Ing. (Nuclear Engineering))--North-West University, Potchefstroom Campus, 2010
9

Reliable Centered Maintenance (RCM) Reliable and Risk Centered Maintenance (RRCM) in Offshore Wind Farms (Case Study- Sweden)

Manouchehrabadi, Maryam Kharaji January 2011 (has links)
Wind power, as a source of renewable energy, is growing very fast. Especially so, is consideration given to offshore wind farms where expansion is due in part to limited social and visual impact, reduced noise effect of turbines, and at the same time higher production of offshore wind turbines. Maintenance is always a considerable and costly part of the wind power investment, especially for offshore projects, but it could not improve as fast as the increasing wind industry in the world. The operation and maintenance management of wind farms should have always a reliable and structured planning to have an economical investment. At the beginning of the growth of wind industry, companies tried to transfer responsibilities of the failure and loss of production to the insurance companies, but it cannot be continued any more. These days even the insurance companies ask about regular inspection or condition monitoring. In other words, they ask for a reliable strategy for operation and maintenance. Both preventative and corrective maintenance are used in offshore wind farms. Preventive maintenance is usually performed at the first sign of failure, and in so doing it helps reduce costs associated from lost production. Having a perfect preventive maintenance program is not easy and it usually needs more inspection and online monitoring. To select a suitable strategy, data should be gathered from different stakeholders who are involved in the project. The stakeholders could be turbine designers, construction companies, transportation companies, operation staff, etc. The reason is that each group has the data which could help to define a reliable strategy of maintenance. Reliability includes measurements, e.g., failure rate, repair time, and availability. Reliability is the ability of components or system to perform their function under given operational condition and for a predicted period of time. However always preventive maintenance especially for offshore wind farm is faced with uncertainty due to bad weather, access difficulty, and logistic limitation. Reliability Centered Maintenance (RCM) is a systematic qualitative technique that balances preventive and corrective maintenance. It chooses the right preventive maintenance activities for the right component at the right time to reach the most cost efficient solution. This research points out that RCM, as an experienced methodology in other industries, could be a good method for scheduled preventive maintenance in offshore wind power for purposes of lowering cost while improving reliability and safety. RCM implementation is always facing with uncertainty. Engaged uncertainty to RCM is known as Reliability and Risk Centered Maintenance RRCM and it could lead maintenance process to an optimal preventive schedule with minimum uncertainty.
10

Design and Evaluation of a Reliable Group Communication Protocol / Design och utvärdering av ett protokoll för tillförlitlig gruppkommunikation

Albin, Odervall, Philip, Montalvo January 2016 (has links)
In distributed systems it is often useful to ensure that messages sent between processes in a group are received by all group members. This thesis presents Reliable Non-Ordered Multicast Protocol (RNOMP). We argue that it achieves reliable multicast between processes in groups that processes can leave and join arbitrarily. The protocol has been implemented on top of a group membership simulation which allows evaluation of the performance of the protocol while varying packet loss and the frequency at which processes leaves and joins groups. After analyzing how the protocol handles certain situations we conclude that our protocol achieves reliability and performs well within certain parameter values.

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