37 research outputs found
User-defined Code generation from UML 2.0
This thesis explores ways to implement transformations from UML 2.0 to code in such a way that the generated code can be customized and extended in a compact and user-friendly way.
As a solution to this problem I introduce a general transformation architecture. The architecture uses an intermediate meta-model in two parts and the transformations are split into manageable, reusable modules.
An example scenario is implemented by two different approaches. Two different intermediate meta-models are implemented and in each case the general transformation architecture is adapted to the specific scenario.
Finally I show examples of how the generated code can be customized by extending or replacing parts of the transformation architecture
Drillstring Washout Diagnosis Using Friction Estimation and Statistical Change Detection
In oil and gas drilling, corrosion or tensile stress can give small holes in the drillstring, which can cause leakage and prevent sufficient flow of drilling fluid. If such \emph{washout} remains undetected and develops, the consequence can be a complete twist-off of the drillstring.
Aiming at early washout diagnosis, this paper employs an adaptive observer to estimate friction parameters in the nonlinear process. Non-Gaussian noise is a nuisance in the parameter estimates, and dedicated generalized likelihood tests are developed to make efficient washout detection with the multivariate -distribution encountered in data. Change detection methods are developed using logged sensor data from a horizontal 1400 m managed pressure drilling test rig. Detection scheme design is conducted using probabilities for false alarm and detection to determine thresholds in hypothesis tests. A multivariate approach is demonstrated to have superior diagnostic properties and is able to diagnose a washout at very low levels. The paper demonstrates the feasibility of fault diagnosis technology in oil and gas drilling
Fault diagnosis of downhole drilling incidents using adaptive observers and statistical change detection
Downhole abnormal incidents during oil and gas drilling cause costly delays, and may also potentially lead to dangerous scenarios. Different incidents will cause changes to different parts of the physics of the process. Estimating the changes in physical parameters, and correlating these with changes expected from various defects, can be used to diagnose faults while in development. This paper shows how estimated friction parameters and flow rates can be used to detect and isolate the type of incident, as well as isolating the position of a defect. Estimates are shown to be subjected to non-Gaussian, -distributed noise, and a dedicated multivariate statistical change detection approach is used that detects and isolates faults by detecting simultaneous changes in estimated parameters and flow rates. The properties of the multivariate diagnosis method are analyzed, and it is shown how detection and false alarm probabilities are assessed and optimized using data-based learning to obtain thresholds for hypothesis testing. Data from a 1400 m horizontal flow loop is used to test the method, and successful diagnosis of the incidents drillstring washout (pipe leakage), lost circulation, gas influx, and drill bit nozzle plugging are demonstrated
Akupunktur og medikamentelle bivirkninger
Et stadig Þkende antall krefttilfeller i Norge, gir et stadig Þkende antall pasienter som mÄ gjennomgÄ cellegiftbehandling. En vanlig bivirkning ved denne behandlingen er kvalme. Da det per i dag ikke finnes gode nok kvalmestillende medikamenter, sÞker pasientene alternative metoder for Ä lindre symptomene. Blant alternative behandlinger for kvalme er akupunktur Þverst pÄ listen. Vi Þnsker med denne oppgaven Ä gÄ i dybden pÄ hvordan akupunktur kan pÄvirke bivirkninger som fÞlge av cellegiftbehandling, da det ogsÄ er et personlig Þnske for oss Ä kunne bidra til Ä lindre symptomer for denne pasientgruppen. I oppgaven har vi tatt for oss problemstillingen: Hvordan kan akupunktur pÄvirke bivirkninger som fÞlge av cellegiftbehandling? -med fokus pÄ kvalme hos kreftpasienter. For Ä belyse problemstillingen har vi benyttet dybdeintervju som metode. Det har blitt utfÞrt sÞk i databaser, og benyttet Tradisjonell Kinesisk Medisinsk (TKM) litteratur fra hÞyskolens pensumliste. I teorikapittelet presenterer vi kvalme sett fra et vestlig medisinsk perspektiv og hva forfatterne sier i TKM. Vi har i tillegg sett pÄ tre forskjellige studier for Ä se hva forskning sier om temaet, samt intervjuet to informanter for Ä fÄ hÞre en akupunktÞrs erfaring fra klinisk praksis. Det vi konkluderer med i denne oppgaven er at det er nÞdvendig med flere enn ett akupunkturpunkt for Ä behandle kvalme som fÞlge av cellegiftbehandling. Denne vurderingen er gjort ut ifra resultatene som er kommet fram av forskning og intervju med informanter
Incident detection and isolation in drilling using analytical redundancy relations
Early diagnosis of incidents that could delay or endanger a drilling operation for oil or gas is essential to limit field development costs. Warnings about downhole incidents should come early enough to allow intervention before it develops to a threat, but this is difficult, since false alarms must be avoided. This paper employs model-based diagnosis using analytical redundancy relations to obtain residuals which are affected differently by the different incidents. Residuals are found to be non-Gaussian - they follow a multivariate -distribution - hence, a dedicated generalized likelihood ratio test is applied for change detection. Data from a 1400 meter horizontal flow loop test facility is used to assess the diagnosis method.
Diagnosis properties of the method are investigated assuming either with available downhole pressure sensors through wired drill pipe or with only topside measurements available. In the latter case, isolation capability is shown to be reduced to group-wise isolation, but the method would still detect all serious events with the prescribed false alarm probability
Drillstring Washout Diagnosis Using Friction Estimation and Statistical Change Detection
Model-Based Diagnosis of Drilling Incidents
Oil and gas drilling is an advanced process with very little instrumentation, where
drilling uid is transported through rotating drillstrings of up to several kilometers,
possibly at extreme depths with high pressure and temperature. A drilling bit is
used at the bottom of the drillstring to crush the formation, and the drilling uid is
used to carry the cuttings to the surface, as well as maintain the pressure in the well.
Drilling is a costly operation, especially o
shore. Incidents can occur that may slow
down the progress. Detecting such incidents manually, especially those occurring
down in the well, may be di cult. Early symptoms may give small variations in
pressure, temperature, and ow rates, possibly covered in measurement noise.
The push for drilling more complex wells in more remote locations demands more
from the drilling control and monitoring system. With advances in drilling control
technology such as managed pressure drilling, and sensor technology such as wired
drill pipe, the complexity of the control system greatly increases. With a high data
rate of sensor readings, as well as lower operation margins, an e cient automatic diagnosis
system is instrumental in reducing operational delays. This thesis presents
di
erent model-based methods for achieving early diagnosis of di
erent drilling incidents,
possibly distinguished from sensor bias, and with estimation of the incident
magnitude. The model-based diagnosis system consists of two parts; rst some
residuals are generated using either adaptive observers or analytical redundancy
relations, then changes to these residuals are detected using a statistical change detection
algorithm, required due to measurement noise. Univariate and multivariate
generalized likelihood ratio tests are applied, using the probability density function
that best matches the noise of the residuals. The thresholds are found using the
probability distribution of the test statistic, determined by a speci ed probability
of false alarms. The probability of fault detection is also found as a function of the
threshold, where data during the incidents are available.
Data from a medium-scale ow loop is used to test the diagnosis method, where
the noise of the residuals ts the t-distribution well. A multivariate change detection
method considering multiple residuals jointly is found to be superior over
a univariate method considering each residual separately, and is used to detect
and isolate the di
erent incidents occurring in the test data. Furthermore, the t-
distribution is shown to give an increased probability of detection compared with
assuming the more common Gaussian distribution. Simulation of a drilling incident
in the high- delity multi-phase simulator OLGA with Gaussian noise in the
measurements is also considered.
The diagnosis framework proposed in this thesis is module-based, where the
methods in each module are simple enough to be implemented in drilling monitoring software at the rig, and can be run in real-time. However, a limitation with the
proposed method is that good data during the normal operating mode is required
for reliable detection and isolation. Future work and implementations should take
this into account, and facilitate automatic acquisition of new data when changes to
the process are made
«Everybody knows how not to cut down a tree»: En iverksettingsstudie av REDD+ -pilotprosjektet i Tanzania
Denne oppgaven har gjennomfĂžrt en evaluering av den norske REDD+ -satsingen i Tanzania. Oppgaven vurderer hvorvidt satsingen har vĂŠrt vellykket, ved Ă„ sette de offentlige mĂ„lsettingene opp mot virkemidlene fra den offentlige strategien. I tillegg til Ă„ bidra til Ă„ nĂ„ generelle utviklingsmĂ„l, har REDD+ -satsingen tre overordnede mĂ„lsettinger, som i fĂžlge Meld. St. 14 (2010â2011) var:
(i) Ă„ bidra til at utslipp fra skog omfattes av et nytt internasjonalt klimaregime. [âŠ], (ii) Ă„ bidra til kostnadseffektive, tidlige og mĂ„lbare reduksjoner i utslipp av klimagasser. [âŠ], [og] (iii) Ă„ bidra til Ă„ ivareta naturskog for Ă„ sikre denne skogen sin evne til Ă„ binde karbon.
Samarbeidet mellom Tanzania og Norge ble inngÄtt med utgangspunkt i en avtale som viker fra disse mÄlene, men da satsingen blir formidlet som REDD+, vil det i et demokratisk perspektiv vÊre interessant Ä se resultatene opp mot de uttalte mÄlsettingene. I en vurdering av virkemiddelbruken for REDD+, kommer det frem at satsingen ikke har oppnÄdd disse, da de sentrale mekanismene for Ä fÄ gjennomfÞre mÄling av utslippsreduksjoner ikke er pÄ plass. Etter en prosjektperiode pÄ fem Är er ikke Tanzania klar for Ä gÄ over til resultatbasert finansiering. Det internasjonale markedet er heller ikke klar for Ä betale for eventuelle reduserte utslippskvoter
Core competence og outsourcing : en litteraturstudie av konseptets spredningsevne og effekter
Avhandlingen er en litteraturstudie av et av de mest populÊre managementkonseptene pÄ 1990- og 2000-tallet; Core Competence. FormÄlet er todelt. For det fÞrste analyserer jeg hvilke oppfatninger som finnes i litteraturen om konseptets opphav, utprÞvdhet og status som organisasjonsoppskrift. For det andre undersÞker jeg hvilke effekter outsourcing - som grep for Ä rendyrke kjernekompetansestrategier - kan ha pÄ organisasjoner. Et sentralt spÞrsmÄl i denne sammenheng, og som ogsÄ tydeliggjÞres i analysen er hvilke forhold som bidrar til at henholdsvis tilsiktede og utilsiktede effekter av outsourcing oppstÄr.
Det viste seg i analysen, at konseptet i litteraturen synes Ä oppfattes som et velutprÞvd redskap for mÄloppnÄelse i organisasjoner. Ved nÊrmere ettersyn oppdaget jeg dog at effektene som tilskrives konseptet i liten grad er empirisk dokumentert i mitt utvalg.
Analysen av effektene outsourcing fÞrer til viste at det for det fÞrste synes Ä vÊre uenighet i faglitteraturen omkring hvorvidt de tilsiktede effektene oppstÄr. Det kan virke som en del av effektene som er forbundet med outsourcing faktisk er overdrevet. I den andre delen denne analysen har jeg vist en rekke faktorer som synes Ä pÄvirke effektene i tilsiktet og utilsiktet retning. Her har jeg vist at trekk ved bakgrunn og prosess i forbindelse med outsourcing i stor grad kan sies Ä pÄvirke utfallet. I tillegg spiller organisasjonskultur en sentral rolle i forbindelse med grepets suksessrate