Tool-supported invariant-based programming

The development of correct programs is a core problem in computer science. Although formal verification methods for establishing correctness with mathematical rigor are available, programmers often find these difficult to put into practice. One hurdle is deriving the loop invariants and proving that the code maintains them. So called correct-by-construction methods aim to alleviate this issue by integrating verification into the programming workflow. Invariant-based programming is a practical correct-by-construction method in which the programmer first establishes the invariant structure, and then incrementally extends the program in steps of adding code and proving after each addition that the code is consistent with the invariants. In this way, the program is kept internally consistent throughout its development, and the construction of the correctness arguments (proofs) becomes an integral part of the programming workflow. A characteristic of the approach is that programs are described as invariant diagrams, a graphical notation similar to the state charts familiar to programmers. Invariant-based programming is a new method that has not been evaluated in large scale studies yet. The most important prerequisite for feasibility on a larger scale is a high degree of automation. The goal of the Socos project has been to build tools to assist the construction and verification of programs using the method. This thesis describes the implementation and evaluation of a prototype tool in the context of the Socos project. The tool supports the drawing of the diagrams, automatic derivation and discharging of verification conditions, and interactive proofs. It is used to develop programs that are correct by construction. The tool consists of a diagrammatic environment connected to a verification condition generator and an existing state-of-the-art theorem prover. Its core is a semantics for translating diagrams into verification conditions, which are sent to the underlying theorem prover. We describe a concrete method for 1) deriving sufficient conditions for total correctness of an invariant diagram; 2) sending the conditions to the theorem prover for simplification; and 3) reporting the results of the simplification to the programmer in a way that is consistent with the invariantbased programming workflow and that allows errors in the program specification to be efficiently detected. The tool uses an efficient automatic proof strategy to prove as many conditions as possible automatically and lets the remaining conditions be proved interactively. The tool is based on the verification system PVS and i uses the SMT (Satisfiability Modulo Theories) solver Yices as a catch-all decision procedure. Conditions that were not discharged automatically may be proved interactively using the PVS proof assistant. The programming workflow is very similar to the process by which a mathematical theory is developed inside a computer supported theorem prover environment such as PVS. The programmer reduces a large verification problem with the aid of the tool into a set of smaller problems (lemmas), and he can substantially improve the degree of proof automation by developing specialized background theories and proof strategies to support the specification and verification of a specific class of programs. We demonstrate this workflow by describing in detail the construction of a verified sorting algorithm. Tool-supported verification often has little to no presence in computer science (CS) curricula. Furthermore, program verification is frequently introduced as an advanced and purely theoretical topic that is not connected to the workflow taught in the early and practically oriented programming courses. Our hypothesis is that verification could be introduced early in the CS education, and that verification tools could be used in the classroom to support the teaching of formal methods. A prototype of Socos has been used in a course at ��bo Akademi University targeted at first and second year undergraduate students. We evaluate the use of Socos in the course as part of a case study carried out in 2007.

Kompressoriyksik��iden mekaaninen kunnonhallinta

Kunnossapidon kuluista suurimman osan aiheuttavat koneiden ennakoimattomat rikkoutumiset ja niiden tuomat tuotannonpys��ytykset. Kunnossapidon suunnitelmallisuutta ja vikojen ennustettavuutta pyrit����n parantamaan erilaisin kunnonvalvonnallisin keinoin. Havaitsemalla alkava vikaantuminen ajoissa ja seuraamalla sen kehittymist�� luodaan mahdollisuus korjaustoimenpiteiden ja -ajankohdan hallittuun suunnitteluun ja t��t�� kautta kustannuss����st��ihin. T��ss�� ty��ss�� on tutkittu kompressoriyksik��iden (kaasuturbiini ja keskipakokompressori) ja niiden apulaitteiden kunnossapidon menetelmi��, niiden hy��dynnett��vyytt�� sek�� mahdollisuuksia kehitt���� mekaanista kunnonhallintaa. Ty��ss�� p����dyttiin johtop����t��kseen, ett�� k��ytett��vien menetelmien hy��dynnett��vyydess�� on kehitett��v����. Kunnonvalvonnan ohjeistuksia tarkennettiin vastaamaan t��m��n p��iv��n tavoitteita. Todettiin my��s, ett�� v��r��htelynvalvontaan perustuva kunnonvalvontaj��rjestelm�� soveltuu hyvin kompressoriyksik��iden kunnonvalvonnan j��rjestelm��ksi. V��r��htelynvalvontaan perustuva kunnonvalvontaj��rjestelm�� luo mahdollisuuden turvallisen k��ytt��ajan ennustamiseen. Kunnonvalvonnan kehitt��misen ja k��ytt��varmuuden parantamisen kannalta jatkotutkimuksen tekeminen kompressoriyksik��iden mekaanistenlaitteiden turvallisen k��ytt��ajan ennustamiseksi on perusteltua.

Mittaukset kostean h��yryn turbiineille

Diplomity��n tavoitteena oli selvitt���� Loviisan ydinvoimalaitoksen h��yryturbiinin suoritus-kyvyn mittaamiseen k��ytett��viss�� olevia menetelmi�� ja mittausj��rjestelmi��. Tavoitteena oli selvitt���� mitk�� tekij��t aiheuttavat mittauksiin mittausvirheit�� ja tutkia turbiineiden nykyisten mittalaitteiden ep��varmuudet. T��ss�� diplomity��ss�� selvitettiin millaisia standardinmukaisia testej�� sek�� muita varteenotettavia testej�� turbiinin suorituskyvyn m����ritt��miseen on k��ytetty ja millaisia mittauksia ne vaativat. Lis��ksi tutkittiin eri l��hteist�� millaisia mittalaitteita ja mittausj��rjestelmi�� voidaan k��ytt���� turbiinin toiminnan mittauksiin. Soveltuvista mittausmenetelmist�� esitettiin toimintaperiaatteet ja teoria. Kunnonvalvontaa varten esiteltiin v��r��htelyiden ja v����nt��-momentin mittaamisen periaatteet. Ep��varmuuksia arvioitiin mittalaitteiden teoreettisen ep��varmuuden ja laitesijoittelun pohjalta. Ty��ss�� havaittiin, ett�� suorituskyvyn arvioimiseksi on olemassa useita standardeja, mutta niiden mukaisiin mittauksiin tarvittaisiin nykyist�� enemm��n mittaustuloksia. Tarkkoja sek�� luotettavia mittaustuloksia on haasteellista saada kaksifaasivirtauksesta. Mittalaitevalinnoilla ja mittalaitteiden m����r���� lis����m��ll�� voidaan mittausten ep��varmuutta pienent����. Loviisan ydinvoimalaitokselle ehdotettiin muutamia mittausj��rjestelmi�� turbiinin suoritus-kyvyn m����ritt��miseksi. Erityisesti turbiinin sis��iset olosuhteet tulisi m����ritt���� nykyist�� tarkemmin. V����nt��momentin mittaaminen olisi hyv�� kunnonvalvonnan ty��kalu.

Monitoring of centrifugal pump operation by a frequency converter

Centrifugal pumps are widely used in industrial and municipal applications, and they are an important end-use application of electric energy. However, in many cases centrifugal pumps operate with a significantly lower energy efficiency than they actually could, which typically has an increasing effect on the pump energy consumption and the resulting energy costs. Typical reasons for this are the incorrect dimensioning of the pumping system components and inefficiency of the applied pump control method. Besides the increase in energy costs, an inefficient operation may increase the risk of a pump failure and thereby the maintenance costs. In the worst case, a pump failure may lead to a process shutdown accruing additional costs. Nowadays, centrifugal pumps are often controlled by adjusting their rotational speed, which affects the resulting flow rate and output pressure of the pumped fluid. Typically, the speed control is realised with a frequency converter that allows the control of the rotational speed of an induction motor. Since a frequency converter can estimate the motor rotational speed and shaft torque without external measurement sensors on the motor shaft, it also allows the development and use of sensorless methods for the estimation of the pump operation. Still today, the monitoring of pump operation is based on additional measurements and visual check-ups, which may not be applicable to determine the energy efficiency of the pump operation. This doctoral thesis concentrates on the methods that allow the use of a frequency converter as a monitoring and analysis device for a centrifugal pump. Firstly, the determination of energy-efficiency- and reliability-based limits for the recommendable operating region of a variable-speed-driven centrifugal pump is discussed with a case study for the laboratory pumping system. Then, three model-based estimation methods for the pump operating location are studied, and their accuracy is determined by laboratory tests. In addition, a novel method to detect the occurrence of cavitation or flow recirculation in a centrifugal pump by a frequency converter is introduced. Its sensitivity compared with known cavitation detection methods is evaluated, and its applicability is verified by laboratory measurements for three different pumps and by using two different frequency converters. The main focus of this thesis is on the radial flow end-suction centrifugal pumps, but the studied methods can also be feasible with mixed and axial flow centrifugal pumps, if allowed by their characteristics.

Techno-Economic Feasibility of Novel On-Line Condition Monitoring Methods in Low Voltage Distribution Networks

The focus in this thesis is to study both technical and economical possibilities of novel on-line condition monitoring techniques in underground low voltage distribution cable networks. This thesis consists of literature study about fault progression mechanisms in modern low voltage cables, laboratory measurements to determine the base and restrictions of novel on-line condition monitoring methods, and economic evaluation, based on fault statistics and information gathered from Finnish distribution system operators. This thesis is closely related to master���s thesis ���Channel Estimation and On-line Diagnosis of LV Distribution Cabling���, which focuses more on the actual condition monitoring methods and signal theory behind them.

Scheduling of guarded command based models

Formal methods provide a means of reasoning about computer programs in order to prove correctness criteria. One subtype of formal methods is based on the weakest precondition predicate transformer semantics and uses guarded commands as the basic modelling construct. Examples of such formalisms are Action Systems and Event-B. Guarded commands can intuitively be understood as actions that may be triggered when an associated guard condition holds. Guarded commands whose guards hold are nondeterministically chosen for execution, but no further control flow is present by default. Such a modelling approach is convenient for proving correctness, and the Refinement Calculus allows for a stepwise development method. It also has a parallel interpretation facilitating development of concurrent software, and it is suitable for describing event-driven scenarios. However, for many application areas, the execution paradigm traditionally used comprises more explicit control flow, which constitutes an obstacle for using the above mentioned formal methods. In this thesis, we study how guarded command based modelling approaches can be conveniently and efficiently scheduled in different scenarios. We first focus on the modelling of trust for transactions in a social networking setting. Due to the event-based nature of the scenario, the use of guarded commands turns out to be relatively straightforward. We continue by studying modelling of concurrent software, with particular focus on compute-intensive scenarios. We go from theoretical considerations to the feasibility of implementation by evaluating the performance and scalability of executing a case study model in parallel using automatic scheduling performed by a dedicated scheduler. Finally, we propose a more explicit and non-centralised approach in which the flow of each task is controlled by a schedule of its own. The schedules are expressed in a dedicated scheduling language, and patterns assist the developer in proving correctness of the scheduled model with respect to the original one.

Vibration analysis for Bearing outer race condition diagnostics

This paper investigates defect detection methodologies for rolling element bearings through vibration analysis. Specifically, the utility of a new signal processing scheme combining the High Frequency Resonance Technique (HFRT) and Adaptive Line Enhancer (ALE) is investigated. The accelerometer is used to acquire data for this analysis, and experimental results have been obtained for outer race defects. Results show the potential effectiveness of the signal processing technique to determine both the severity and location of a defect. The HFRT utilizes the fact that much of the energy resulting from a defect impact manifests itself in the higher resonant frequencies of a system. Demodulation of these frequency bands through use of the envelope technique is then employed to gain further insight into the nature of the defect while further increasing the signal to noise ratio. If periodic, the defect frequency is then present in the spectra of the enveloped signal. The ALE is used to enhance the envelope spectrum by reducing the broadband noise. It provides an enhanced envelope spectrum with clear peaks at the harmonics of a characteristic defect frequency. It is implemented by using a delayed version of the signal and the signal itself to decorrelate the wideband noise. This noise is then rejected by the adaptive filter that is based upon the periodic information in the signal. Results have been obtained for outer race defects. They show the effectiveness of the methodology to determine both the severity and location of a defect. In two instances, a linear relationship between signal characteristics and defect size is indicated.

Experimental validation of a 3-D vision-based measurement system applied to robot calibration

One of the problems that slows the development of off-line programming is the low static and dynamic positioning accuracy of robots. Robot calibration improves the positioning accuracy and can also be used as a diagnostic tool in robot production and maintenance. A large number of robot measurement systems are now available commercially. Yet, there is a dearth of systems that are portable, accurate and low cost. In this work a measurement system that can fill this gap in local calibration is presented. The measurement system consists of a single CCD camera mounted on the robot tool flange with a wide angle lens, and uses space resection models to measure the end-effector pose relative to a world coordinate system, considering radial distortions. Scale factors and image center are obtained with innovative techniques, making use of a multiview approach. The target plate consists of a grid of white dots impressed on a black photographic paper, and mounted on the sides of a 90-degree angle plate. Results show that the achieved average accuracy varies from 0.2mm to 0.4mm, at distances from the target from 600mm to 1000mm respectively, with different camera orientations.

Paperitehtaan arkittamon kokonaistehokkuuden nostaminen kunnossapitoa kehitt��m��ll��

T��m��n diplomity��n tavoitteena oli tutkia, miten UPM:n Kymin tehtaan A4- arkittamon kunnossapitotoimintaa pystytt��isiin kehitt��m����n niin, ett�� tuotantolaitoksen kokonaistehokkuutta saataisiin kasvatettua. Ty��ss�� on pohdittu keinoja nykyisen, p����asiallisesti korjaavan kunnossapitotoiminnan muuttamiseksi suunnitelmalliseksi eri teorial��ht��kohtien pohjalta. Keskeinen teoria, johon ty��n tulokset pohjautuvat, on kokonaisvaltainen tuottava kunnossapito (TPM). Kirjallisuusl��hteisiin tukeutuvaa tutkimusta t��ydensiv��t useat haastattelut, A4-valmistajille suunnattu laitteiden kuntokartoituskysely ja tuotannon- ja toiminnanohjausj��rjestelmist�� ker��tty mittausaineisto. Ty��n merkitt��vimm��t tulokset osoittavat, ett�� A4-arkittamon kunnossapitotoimintaa tulisi suunnata nykyist�� enemm��n k��ytt��kunnossapitol��ht��iseksi. K��ytt��kunnossapito perustuu tuotannon operaattoreiden osallistumiseen kunnossapitotoimiin varsinaisen kunnossapitohenkil��st��n ohella. Tuotantooperaattoreilla on ty��ns�� vuoksi parhaat mahdollisuudet k��ytt��miens�� laitteiden kunnonvalvontaan ja n��in ollen mahdollisten vikaantumisten ennakointiin jo varhaisessa vaiheessa. Ennakoimalla pystytt��isiin parantamaan kunnossapidon suunnitelmallisuutta, mink�� ansiosta laitteiden k��ytett��vyys ja sit�� kautta tuotantolaitoksen kokonaistehokkuus olisivat nykyist�� korkeampia.

Customer knowledge processing in maintenance business: case study

The purpose of the study is to examine and increase knowledge on customer knowledge processing in B2B context from sales perspective. Further objectives include identifying possible inhibiting and enabling factors in each phase of the process. The theoretical framework is based on customer knowledge management literature. The study is a qualitative study, in which the research method utilized is a case study. The empirical part was implemented in a case company by conducting in-depth interviews with the company���s value-selling champions located internationally. Context was maintenance business. Altogether 17 interviews were conducted. The empirical findings indicate that customer knowledge processing has not been clearly defined within the maintenance business line. Main inhibiting factors in acquiring customer knowledge are lack of time and vast amount of customer knowledge received. Enabling factors recognized are good customer relationships and sales representatives��� communication skills. Internal dissemination of knowledge is mainly inhibited by lack of time and restrictions in customer relationship management systems. Enabling factors are composition of the sales team and updated customer knowledge. Inhibiting utilization is lack of goals to utilize the customer knowledge and a low quality of the knowledge. Moreover, customer knowledge is not systematically updated nor analysed. Management of customer knowledge is based on the CRM system. As implications of the study, it is suggested for the case company to define customer knowledge processing in order to support maintenance business process.

Elintarviketehtaan tuotantolinjan kunnonvalvonnan kehitt��minen

Tutkimuksen tavoitteena oli kunnonvalvontaj��rjestelm��n kehitt��minen nykyaikaiselle elintarviketeollisuuden tuotantolinjalle. Ty��ss�� etsittiin olemassa olevia kunnonvalvontamenetelmi�� ja -sovelluksia erityisesti j����tel��tuotantolaitteiden tarpeisiin. Kirjallisuudesta l��ydettiin sovelluksia l��hinn�� yksitt��isille komponenteille ja kone-elimille. Tutkimuksen kohteena oleva tuotantolinja k��ytiin l��pi toimintojen ja komponenttien osalta. Tehtaan laitekantaa ja valmiutta kunnonvalvonnan k��ytt����notolle k��siteltiin yleisell�� tasolla. Kunnonvalvontaj��rjestelm���� kehitett��ess�� k��ytettiin hyv��ksi kirjallisuudesta l��ytyneit�� menetelmi��, joista soveltuvimpia k��ytettiin kunnonvalvontametodien kartoittamiseen. Kunnonvalvontametodit muodostettiin toiminnanohjausj��rjestelm��st�� ja linjan k��ytt����notosta saatujen tietojen avulla. Tietoja k��ytettiin vika-vaikutusanalyysiss��, joka oli pohjana komponentti- ja menetelm��kohtaisessa analyysissa. Kriittisi�� ja tuotannon tehokkuuteen vaikuttavia koneenosia ja kokonaisuuksia tarkasteltiin kunnonvalvontamenetelmien soveltuvuuden avulla. Tutkimuksen edetess�� kehitettiin kokonaisvaltaiset toiminnanohjausj��rjestelm��n avulla toimivat eritasoiset kunnonvalvontahypoteesit, joiden avulla linjan yksitt��isten komponenttien kuntoa voidaan valvoa. Lis��ksi tutkimuksessa kehitettiin uusia kunnonvalvontasovelluksia, joita on mahdollista k��ytt���� my��s tehtaan muilla linjoilla. Kunnonvalvontahypoteeseja k��ytettiin kokonaisen kunnonvalvontaj��rjestelm��n luomiseen. Tehtaalla on mahdollisuus valita k��ytt����notettavan kunnonvalvonnan taso hypoteesien sek�� kunnossapitostrategian avulla.

Seasonal variation in migratory body condition, corticosterone secretion, oxidative stress and biotransformation activity in barn swallows (Hirundo rustica L.)

I studied the associations between migration-related physiological regulation (corticosterone) and body condition of barn swallows (Hirundo rustica L.). An additional purpose was to determine whether oxidative stress and biotransformation activity vary seasonally. Since physiological regulation, biotransformation activity and the stress involved may be important factors for body condition during migration; they may have direct effects on migration success. This in turn may influence other important life history stages, such as breeding and moult. In the thesis I used barn swallow data of the Finnish Ringing Centre (1997���2009), consisting of all juveniles ringed in the nests and recaptured from night roosts later the same autumn. Before the autumn migration in Finland I also captured, ringed and sampled barn swallows from night roosts in 2003, 2006, 2007 and 2011. Samples preceding spring migration in South Africa were collected in 2007. Juvenile barn swallows started to migrate southward in mid-August (first broods). Second broods started their migration at a younger age and almost a month later than first broods (mid-September). Barn swallows increased body mass and accumulated fat for the autumn migration. In the course of the autumn they seemed to be able to prevent the loss of energy already accumulated, since the proportional overnight mass loss, fat loss and faecal production decreased. Surprisingly, corticosterone, the major energy-regulating hormone in birds, seemed not to be involved in the fuelling process. Previous studies with warblers, sparrows and shorebirds had shown that during migration, the baseline levels of corticosterone were elevated in order to facilitate fuelling. It is possible that for Finnish barn swallows the most important fuelling place is in southern Europe, since northern and eastern populations migrate via the Balkan Peninsula. However, the adrenocortical stress response of Finnish barn swallows in good body condition was lower than that of those in poor body condition. Birds clearly suppressed the response, probably to prevent the catabolic effects of excessive corticosterone levels; birds cannot afford to lose muscle mass before migration. South African barn swallows had high levels of baseline corticosterone, but this may have been associated with the high oxidative damage and biotransformation activity of those birds. Barn swallows in spring and summer had low biotransformation activity and intermediate oxidative stress, which was probably related to breeding. Autumn birds had low biotransformation activity and oxidative stress but high redox enzyme activities in some migration-related enzymes.

Growth and development of honey weed based on days or thermal units

This work was carried out with the objective of evaluating the growth and development of honey weed (Leonurus sibiricus) based on days or thermal units (growing degree days). Thus, two independent trials were developed to quantify the phenological development and total dry mass accumulation in increasing or decreasing photoperiod conditions. Considering only one growing season, honey weed phenological development was perfectly fit to day scale or growing degree days, but with no equivalence between seasons, with the plants developing faster at increasing photoperiods, and flowering 100 days after seeding. Even day-time scale or thermal units were not able to estimate general honey weed phenology during the different seasons of the year. In any growing condition, honey weed plants were able to accumulate a total dry mass of over 50 g per plant. Dry mass accumulation was adequately fit to the growing degree days, with highlights to a base temperature of 10 ��C. Therefore, a higher environmental influence on species phenology and a lower environmental influence on growth (dry mass) were observed, showing thereby that other variables, such as the photoperiod, may potentially complement the mathematical models.