Väsyttävästi kuormitettujen hitsattujen rakenteiden suunnittelukäytännön kehittäminen

Hitsatuilla rakenteilla väsyminen on keskeinen vauriotekijä. Väsymiskestoiän laskentaan on olemassa useita erilaisia menetelmiä, joista hot spot ﷓menetelmä on hitsattujen rakenteiden yhteydessä yhä yleistyvä ja sangen käyttökelpoinen. Hot spot menetelmässä kestoikälaskenta perustuu rakenteellisen jännityksen vaihteluun ja pieneen joukkoon kokeellisesti määrättyjä Wöhler-käyriä. Rakenteellinen jännitys voidaan määrittää joko prototyypistä mittaamalla, elementtimenetelmällä laskemalla tai parametristen kerrointen avulla. Suunnittelukäytännön kehittämisessä tutkittiin esimerkkirakenteena Rammer RC 22 leikkurimurskainta. Tarkoituksena oli mitata murskaimesta voimasuureita, joita voitaisiin käyttää kuormitustietona laskettaessa jännityksiä elementtimenetelmällä. Myöhempien laskentatulosten verifiointia varten mitattiin lisäksi muutamia hot spot ﷓jännityksiä. Työn kokeellinen puoli keskittyi voimasuuremittauksiin ja niistä saatavien tulosten saattamiseen sopusointuun vapaakappalemallien kanssa. Suoritettiin lukuisia kalibrointimittauksia ja mittausjärjestelyä kehitettiin, kunnes syyt aluksi saatujen mittaustulosten virheellisyyteen selvisivät. Leikkausvoimamittausten osalta tuloksia verifioitiin elementtimenetelmälaskelmin. Työn tuloksena saatiin luotua toimiva pohja voimasuure- ja hot spot ﷓mittauksille. Jatkossa voidaan siirtyä tekemään mittauksia todellisissa työskentelytilanteissa.

Kunnossapitohitsaus vaneritehtaassa

Diplomityöni tavoitteena on selvittää mekaanisen puunjalostuksen kunnossapitohitsauksessa huomioitavat asiat ja laatia niiden pohjalta vaneritehtaan käyttöön kunnossapitohitsauksen ohjeistus. Diplomityössä käsiteltiin yhtä kunnossapidon aluetta, hitsausta. Työssä esiteltiin erilaisia hitsaukseen liittyviä määritelmiä ja menetelmiä. Käytännön kokeet oli valittu esimerkkitehtaalle tärkeistä kohteista. Diplomityö tehtiin vaneriteollisuuden koneita suunnittelevaan ja toimittavaan yritykseen. Käytännön kokeet suoritettiin toimivassa vaneritehtaassa. Teoriaosassa keskityttiin sellaisiin osa - alueisiin, jotka liittyvät vaneritehtaan jokapäiväiseen kunnossapitohitsaukseen. Käytännön osuudessa havaittiin tiettyjä kokeesta toiseen toistuvia puutteita. Tällaisia olivat mm. vajaa hitsautumissyvyys, lisäaineiden käsittely, puikon koon valinta ja railon valmistus. Näiden seikkojen kautta vahvistui käsitys ohjeistuksen tarpeellisuudesta, joka oli jo työn tavoitteissa yhtenä päämääränä. Ongelmia esiintyi myös eräiden materiaalien hitsauksessa. Tämä alue tulee hoitaa kuntoon koulutuksella pikimmiten. Tilanne esimerkkitehtaassa kunnossapitohitsauksen osalta oli parempi kuin alun perin oletettiin. Muutamien puutteiden poistamisen, ohjeistuksen ja koulutuksen jälkeen tilanne tulee olemaan hyvä. Innostusta hitsauksen salojen selville saamiseen on kunnossapidon työntekijöiden joukossa.

Evaluation of Teacher Education Programs by Students and Graduates

The purpose of this research was to do a repeated cross-sectional research on class teachers who study in the 4th year and also graduated at the Faculty of Education, University of Turku between the years of 2000 through 2004. Specifically, seven research questions were addressed to target the main purpose of the study: How do class teacher education masters’ degree senior students and graduates rate “importance; effectiveness; and quality” of training they have received at the Faculty of Education? Are there significant differences between overall ratings of importance; effectiveness and quality of training by year of graduation, sex, and age (for graduates) and sex and age (for senior students)? Is there significant relationship between respondents’ overall ratings of importance; effectiveness and their overall ratings of the quality of training and preparation they have received? Are there significant differences between graduates and senior students about importance, effectiveness, and quality of teacher education programs? And what do teachers’ [Graduates] believe about how increasing work experience has changed their opinions of their preservice training? Moreover the following concepts related to the instructional activities were studied: critical thinking skills, communication skills, attention to ethics, curriculum and instruction (planning), role of teacher and teaching knowledge, assessment skills, attention to continuous professional development, subject matters knowledge, knowledge of learning environment, and using educational technology. Researcher also tried to find influence of some moderator variables e.g. year of graduation, sex, and age on the dependent and independent variables. This study consisted of two questionnaires (a structured likert-scale and an open ended questionnaire). The population in study 1 was all senior students and 2000-2004 class teacher education masters’ degree from the departments of Teacher Education Faculty of Education at University of Turku. Of the 1020 students and graduates the researcher was able to find current addresses of 675 of the subjects and of the 675 graduates contacted, 439 or 66.2 percent responded to the survey. The population in study 2 was all class teachers who graduated from Turku University and now work in the few basic schools (59 Schools) in South- West Finland. 257 teachers answered to the open ended web-based questions. SPSS was used to produce standard deviations; Analysis of Variance; Pearson Product Moment Correlation (r); T-test; ANOVA, Bonferroni post-hoc test; and Polynomial Contrast tests meant to analyze linear trend. An alpha level of .05 was used to determine statistical significance. The results of the study showed that: A majority of the respondents (graduates and students) rated the overall importance, effectiveness and quality of the teacher education programs as important, effective and good. Generally speaking there were only a few significant differences between the cohorts and groups related to the background variables (gender, age). The different cohorts were rating the quality of the programs very similarly but some differences between the cohorts were found in the importance and effectiveness ratings. Graduates of 2001 and 2002 rated the importance of the program significantly higher than 2000 graduates. The effectiveness of the programs was rated significantly higher by 2001 and 2003 graduates than other groups. In spite of these individual differences between cohorts there were no linear trends among the year cohorts in any measure. In respondents’ ratings of the effectiveness of teacher education programs there was significant difference between males and females; females rated it higher than males. There were no significant differences between males’ and females’ ratings of the importance and quality of programs. In the ratings there was only one difference between age groups. Older graduates (35 years or older) rated the importance of the teacher training significantly higher that 25-35 years old graduates. In graduates’ ratings there were positive but relatively low correlations between all variables related to importance, effectiveness and quality of Teacher Education Programs. Generally speaking students’ ratings about importance, effectiveness and quality of teacher education program were very positive. There was only one significant difference related to the background variables. Females rated higher the effectiveness of the program. The comparison of students’ and graduates’ perception about importance, effectiveness, and quality of teacher education programs showed that there were no significant differences between graduates and students in the overall ratings. However there were differences in some individual variables. Students rated higher in importance of “Continuous Professional Development”, effectiveness of “Critical Thinking Skills” and “Using Educational Technology” and quality of “Advice received from the advisor”. Graduates rated higher in importance of “Knowledge of Learning Environment” and effectiveness of “Continuous Professional Development”. According to the qualitative data of study 2 some graduates expressed that their perceptions have not changed about the importance, effectiveness, and quality of training that they received during their study time. They pointed out that teacher education programs have provided them the basic theoretical/formal knowledge and some training of practical routines. However, a majority of the teachers seems to have somewhat critical opinions about the teacher education. These teachers were not satisfied with teacher education programs because they argued that the programs failed to meet their practical demands in different everyday situations of the classroom e.g. in coping with students’ learning difficulties, multiprofessional communication with parents and other professional groups (psychologists and social workers), and classroom management problems. Participants also emphasized more practice oriented knowledge of subject matter, evaluation methods and teachers’ rights and responsibilities. Therefore, they (54.1% of participants) suggested that teacher education departments should provide more practice-based courses and programs as well as closer collaboration between regular schools and teacher education departments in order to fill gap between theory and practice.

A Co-Processor Approach for Efficient Java Execution in Embedded Systems

This thesis deals with a hardware accelerated Java virtual machine, named REALJava. The REALJava virtual machine is targeted for resource constrained embedded systems. The goal is to attain increased computational performance with reduced power consumption. While these objectives are often seen as trade-offs, in this context both of them can be attained simultaneously by using dedicated hardware. The target level of the computational performance of the REALJava virtual machine is initially set to be as fast as the currently available full custom ASIC Java processors. As a secondary goal all of the components of the virtual machine are designed so that the resulting system can be scaled to support multiple co-processor cores. The virtual machine is designed using the hardware/software co-design paradigm. The partitioning between the two domains is flexible, allowing customizations to the resulting system, for instance the floating point support can be omitted from the hardware in order to decrease the size of the co-processor core. The communication between the hardware and the software domains is encapsulated into modules. This allows the REALJava virtual machine to be easily integrated into any system, simply by redesigning the communication modules. Besides the virtual machine and the related co-processor architecture, several performance enhancing techniques are presented. These include techniques related to instruction folding, stack handling, method invocation, constant loading and control in time domain. The REALJava virtual machine is prototyped using three different FPGA platforms. The original pipeline structure is modified to suit the FPGA environment. The performance of the resulting Java virtual machine is evaluated against existing Java solutions in the embedded systems field. The results show that the goals are attained, both in terms of computational performance and power consumption. Especially the computational performance is evaluated thoroughly, and the results show that the REALJava is more than twice as fast as the fastest full custom ASIC Java processor. In addition to standard Java virtual machine benchmarks, several new Java applications are designed to both verify the results and broaden the spectrum of the tests.

Laitepuhdistamon ylijäämäliete ja sen kuiva-ainepitoisuuden nostaminen

Työssä tutkittiin pienpuhdistamon ylijäämälietteen ominaisuuksia ja käyttäytymistä pienpuhdistamon ylijäämälietteen tiivistys- tai kuivausmenetelmän kehittämisen teoriapohjaksi. Työ sisältää myös lietteiden tiivistysmenetelmien kustannustarkastelua. Kokeellisessa osuudessa käytettiin työn teettäjän Oy KWH Pipe Ab:n valmistamien pienpuhdistamojen ylijäämälietettä. Tutkittava ylijäämäliete oli peräisin asukasvastineluvultaan 5–95 pienistä aktiivilietelaitepuhdistamoista. Tiivistys- tai kuivausmenetelmän kehittämisen tarkoituksena on saavuttaa kustannussäästöjä pienpuhdistamon ylijäämälietteen kuljetusmatkojen vähentämisen kautta. Soveltuvia vertailtavia sovelluksia ovat staattiseen laskeuttamiseen perustuvat menetelmät, mekaaniset ruuvi- ja linkokuivaimet, kuivauslava ja flotaatio. Tarkasteltavien menetelmien tuli olla käytöltä ja huollolta sekä käyttökuluiltaan edullisia ja yksinkertaisia. Ylijäämälietteiden ominaisuuksia ja käyttäytymistä tutkittiin kirjallisuuslähteistä ja käytännön kokein. Kokeissa tarkasteltiin ylijäämälietteen laskeutumis- ja nousuominaisuuksia, redox-potentiaalin vaihtelua seisovassa näytteessä ja flotaation onnistumista testattavalle lietteelle. Kokeet tehtiin kullakin kerralla eri ajankohtana otetuille lietenäytteille, käytettyjä puhdistamoja oli useita ja mitoitus, kuormitus sekä jäteveden laatu vaihteli paljon.

Drug loading of mesoporous silicon particles

Porous silicon (PSi) is a promising material to be utilized in drug delivery formulations. The release rate of the drug compound can be controlled by changing the pore properties and surface chemistry of PSi. The loading of a poorly soluble drug into mesoporous silicon particles enhances its dissolution in the body. The drug loading is based on adsorption. The attainable maximum loaded amount depends on the properties of the drug compound and the PSi material, and on the process conditions. The loading solvent also essentially affects the adsorption process. The loading of indomethacin into PSi particles with varying surface modification was studied. Solvent mixtures were applied in the loading, and the loaded samples were analyzed with thermal analysis methods. The best degree of loading was obtained using a mixture of dichloromethane and methanol. The drug loads varied from 7.7 w-% to 26.8 w-%. A disturbing factor in the loading experiments was the tendency of indomethacin to form solvates with the solvents applied. In addition, the physical form and stability of indomethacin loaded in PSi and silica particles were studied using Raman spectroscopy. In the case of silica, the presence of crystalline drug as well as the polymorph form can be detected, but the method proved to be not applicable for PSi particles.

Tests of International Asset Pricing Models in Scandinavian Stock Markets

This thesis examines whether global, local and exchange risks are priced in Scandinavian countries’ equity markets by using conditional international asset pricing models. The employed international asset pricing models are the world capital asset pricing model, the international asset pricing model augmented with the currency risk, and the partially segmented model augmented with the currency risk. Moreover, this research traces estimated equity risk premiums for the Scandinavian countries. The empirical part of the study is performed using generalized method of moments approach. Monthly observations from February 1994 to June 2007 are used. Investors’ conditional expectations are modeled using several instrumental variables. In order to keep system parsimonious the prices of risk are assumed to be constant whereas expected returns and conditional covariances vary over time. The empirical findings of this thesis suggest that the prices of global and local market risk are priced in the Scandinavian countries. This indicates that the Scandinavian countries are mildly segmented from the global markets. Furthermore, the results show that the exchange risk is priced in the Danish and Swedish stock markets when the partially segmented model is augmented with the currency risk factor.

Hitsatun kerrossihtilevyrakenteen soveltuvuus sellutehtaan laitteiden suodatinpinnaksi

Tässä diplomityössä tutkittiin hitsaamalla valmistettavan kerrossihtilevyn soveltuvuutta eri sellutehtaan laitteisiin mekaanisen kuormituskokeen, korroosiokokeen ja syrjäytyskokeiden avulla. Tutkimusympäristönä käytettiin puukuitupesuria, sillä kerrossihtilevyrakenteen todennäköisimpiä käyttökohteita ovat erilaiset massan pesuun tarkoitetut laitteet. Mekaanisen kuormituksen kokeessa tarkasteltiin kerrossihtilevyn staattista ja dynaamista kuormituksen kestoa painevaihteluiden avulla pesurin koelokerossa ja verrattiin sitä porattuun reikälevyyn. Kokeessa käytetyn kerrossihtilevyversion todettiin olevan huomattavasti porattua saman paksuista reikälevyä heikompi dynaamisen kuormituksen alaisena. Syrjäytyskokeilla määritettiin syrjäytysnopeus erilaisilla reiänhalkaisijoilla ja –jaoilla sekä tutkittiin väriaineen avulla sokeiden tukikannasten vaikutusta syrjäytyspesun homogeenisuuteen levyn pinnassa. Syrjäytysnopeuden todettiin heikentyvän vapaan reikäpinta-alan pienentyessä. Väriaineellisissa kokeissa ei havaittu tukikannasten merkittävästi alentavan syrjäytysnopeutta. Korroosiokokeilla tutkittiin ja vertailtiin laser- ja vastuspistehitsien korroosionkestokykyä kloridipitoisissa olosuhteissa lämpötilan säätelyn mahdollistavan olosuhdekaapin avulla. Laserhitsauksessa parametrien ei havaittu vaikuttavan merkittävästi hitsin herkistymislämpötilaan. Vastuspistehitsaamalla on mahdollista saavuttaa laserhitsien korroosionkesto.

High pressure compression of filter cakes

The purpose of this thesis was to investigate the compression of filter cakes at high filtration pressures with five different test materials and to compare the energy consumption of high pressure compression with the energy consumption of thermal drying. The secondary target of this study was to investigate the particle deformation of test materials during filtration and compression. Literature part consists of basic theory of filtration and compression and of the basic parameters that influence the filtration process. There is also a brief description about all of the test materials including their properties and their industrial production and processing. Theoretical equations for calculating the energy consumptions of the filtrations at different conditions are also presented. At the beginning of the experiments at experimental part, the basic filtration tests were done with all the five test materials. Filtration tests were made at eight different pressures, from 6 bars up to 100 bars, by using piston press pressure filter. Filtration tests were then repeated by using a cylinder with smaller slurry volume than in the first series of filtration tests. Separate filtration tests were also done for investigating the deformation of solid particles during filtration and for finding the optimal curve for raising the filtration pressure. Energy consumption differences between high pressure filtration and ideal thermal drying process were done partly experimentally and partly by using theoretical calculation equations. By comparing these two water removal methods, the optimal ranges for their use were found considering their energy efficiency. The results of the measurements shows that the filtration rate increased and the moisture content of the filter cakes decreased as the filtration pressure was increased. Also the porosity of the filter cakes mainly decreased when the filtration pressure was increased. Particle deformation during the filtration was observed only with coal particles.

Erikoissähkökoneen tyyppitestaus

Uusien erikoissähkökoneiden testaus perinteisten standardien mukaan on osittain haasteellista. Erikoissähkökoneille, kuten kestomagneettitahtikoneelle ei ole esitetty suoranaisia standardin vaatimia testejä, joten siihen joudutaan soveltamaan olemassa olevia erillismagnetoiduntahtikoneen standardeja. Testien tavoitteena on olla luotettavia sekä vertailukelpoisia. Mittausten on oltava toistettavissa. Mittaustavasta riippuen voidaan saada erilaisia tuloksia, jotka vaikuttavat lopputulokseen. Standardien mukaisessa testauksessa saadaan mittauksista samanlaisia ja samalla saadaan mittausvirheen mahdollisuus pienemmäksi ja tällä tavoin tulokset keskenään vertailukelpoisemmiksi. Tässä työssä tarkastellaan kahta erilaista erikoissähkokonetta, kestomagneettitahtikonetta ja massiiviroottoriepätahtikonetta. Työssä selvitetään standardin IEC 60034 soveltuvuutta tyyppitesteihin, joita kyseiset konetyypit vaativat. Lisäksi työssä vertaillaan standardin IEC 60034 mukaisen hyötysuhteen määrittämistä. Se antaakin useita vaihtoehtoja hyötysuhteen määrittämiselle.

Tietovaraston uudelleensuunnittelu ja toteuttaminen

Tietovarastointi on yleistynyt yritysten raportoinnin tietolähteenä. Tietovarastojen avulla voidaan kehittää monipuolisia raportointiratkaisuja. Datamäärän ja käyttäjämäärän kasvu sekä raporttien monipuolistuminen aiheuttavat suorituskykyhaasteita. Tässä työssä käydään läpi tietovaraston uudelleensuunnittelu suorituskykyhaasteisiin keskittyen. Työn tavoitteena oli sekä tietovaraston käytön että ylläpidon tehostaminen. Työvaiheina olivat arkkitehtuurin kehittäminen, faktan ja dimensioiden optimointi, ETL-prosessin tehostaminen, paikallisvarastojen rakentaminen sekä osioinnin, indeksien ja aggregaatiosummien tehokkaampi hyödyntäminen. Tavoitteen toteutumista mitattiin toistamalla työn eri vaiheissa suorituskykytestejä. Tuloksena saavutettiin merkittävä suorituskyvyn parantuminen erityisesti työn aikana luoduissa paikallisvarastoissa. Tietovarastoon tehtävien kyselyiden ja hallintatoimenpiteiden kesto pieneni yleisesti noin kolmannekseen. Erillisiin käyttötarkoituksiin räätälöityihin paikallisvarastoihin tehtävien kyselyjen kesto pieneni noin kymmenykseen tai parhaassa tapauksessa jopa sadasosaan

A study of combustion phenomena in circulating fluidized beds by developing and applying experimental and modelling methods for laboratory-scale reactors

The results shown in this thesis are based on selected publications of the 2000s decade. The work was carried out in several national and EC funded public research projects and in close cooperation with industrial partners. The main objective of the thesis was to study and quantify the most important phenomena of circulating fluidized bed combustors by developing and applying proper experimental and modelling methods using laboratory scale equipments. An understanding of the phenomena plays an essential role in the development of combustion and emission performance, and the availability and controls of CFB boilers. Experimental procedures to study fuel combustion behaviour under CFB conditions are presented in the thesis. Steady state and dynamic measurements under well controlled conditions were carried out to produce the data needed for the development of high efficiency, utility scale CFB technology. The importance of combustion control and furnace dynamics is emphasized when CFB boilers are scaled up with a once through steam cycle. Qualitative information on fuel combustion characteristics was obtained directly by comparing flue gas oxygen responses during the impulse change experiments with fuel feed. A one-dimensional, time dependent model was developed to analyse the measurement data Emission formation was studied combined with fuel combustion behaviour. Correlations were developed for NO, N2O, CO and char loading, as a function of temperature and oxygen concentration in the bed area. An online method to characterize char loading under CFB conditions was developed and validated with the pilot scale CFB tests. Finally, a new method to control air and fuel feeds in CFB combustion was introduced. The method is based on models and an analysis of the fluctuation of the flue gas oxygen concentration. The effect of high oxygen concentrations on fuel combustion behaviour was also studied to evaluate the potential of CFB boilers to apply oxygenfiring technology to CCS. In future studies, it will be necessary to go through the whole scale up chain from laboratory phenomena devices through pilot scale test rigs to large scale, commercial boilers in order to validate the applicability and scalability of the, results. This thesis shows the chain between the laboratory scale phenomena test rig (bench scale) and the CFB process test rig (pilot). CFB technology has been scaled up successfully from an industrial scale to a utility scale during the last decade. The work shown in the thesis, for its part, has supported the development by producing new detailed information on combustion under CFB conditions.