Michelson interferometer with porch swing bearing for portable FTIR spectrometer

The interferometer for low resolution portable Fourier Transform middle infrared spectrometer was developed and studied experimentally. The final aim was a concept for a commercial prototype. Because of the portability, the interferometer should be compact sized and insensitive to the external temperature variations and mechanical vibrations. To minimise the size and manufacturing costs, Michelson interferometer based on plane mirrors and porch swing bearing was selected and no dynamic alignment system was applied. The driving motor was a linear voice coil actuator to avoid mechanical contact of the moving parts. The driving capability for low mirror driving velocities required by the photoacoustic detectors was studied. In total, four versions of such an interferometer were built and experimentally studied. The thermal stability during the external temperature variations and the alignment stability over the mirror travel were measured using the modulation depth of the wide diameter laser beam. Method for estimating the mirror tilt angle from the modulation depth was developed to take account the effect from the non-uniform intensity distribution of the laser beam. The spectrometer stability was finally studied also using the infrared radiation. The latest interferometer was assembled for the middle infrared spectrometer with spectral range from 750 cm−1 to 4500 cm−1. The interferometer size was (197 × 95 × 79) mm3 with the beam diameter of 25 mm. The alignment stability as the change of the tilt angle over the mirror travel of 3 mm was 5 μrad, which decreases the modulation depth only about 0.7 percent in infrared at 3000 cm−1. During the temperature raise, the modulation depth at 3000 cm−1 changed about 1 . . . 2 percentage units per Celsius over short term and even less than 0.2 percentage units per Celsius over the total temperature raise of 30 °C. The unapodised spectral resolution was 4 cm−1 limited by the aperture size. The best achieved signal to noise ratio was about 38 000:1 with commercially available DLaTGS detector. Although the vibration sensitivity requires still improving, the interferometer performed, as a whole, very well and could be further developed to conform all the requirements of the portable and stable spectrometer.

Aktiivisten magneettilaakereiden ohjauslaitteiston vaatimusmäärittely ja toteutus

Aktiivinen magneettilaakeri on järjestelmä joka mahdollistaa pyörivän kappaleen, esimerkiksi sähkökoneen roottorin, leijuttamisen magneettikentässä ilman fyysistä kontaktia vastakappaleiden välillä. Tekniikalla on joitain merkittäviä etuja muihin laakerointijärjestelmiin verrattuna erityisesti suurnopeuksisissa tai puhdastiloissa käytettävissä sähkökäytöissä. Magneettilaakereiden yleistymistä nopeuttaisi ja niiden hintaa laskisi mikäli laakereiden säätöön ja tehonsyöttöön voitaisiin käyttää standardeja teollisuusautomaatiolaitteita erityisesti tätä käyttötarkoitusta varten kehitettyjen laitteiden sijaan. Tässä työssä luodaan menetelmä määrittää vähimmäisvaatimukset aktiivisen magneettilaakerin säätöalgoritmien suorittamiseen käytetylle säätöjärjestelmälle ja anturoinnille sekä laakerin toimintaan tarvittavalle tehoelektroniikalle. Näiden vaatimusten perusteella luodaan katsaus soveltuviin laitteisiin ja kootaan esimerkkikokoonpanot kahdelle erilaiselle magneettilaakeroitavalle kohteelle. Lisäksi työssä esitellään LUT:ssa vuosina 2014-2015 kehitetty magneettilaakerin teholähdeprototyyppi ja selvitetään edellytykset käyttää laitetta laakerijärjestelmän osana.

Multibody models for examination of touchdown bearing systems

Increased rotational speed brings many advantages to an electric motor. One of the benefits is that when the desired power is generated at increased rotational speed, the torque demanded from the rotor decreases linearly, and as a consequence, a motor of smaller size can be used. Using a rotor with high rotational speed in a system with mechanical bearings can, however, create undesirable vibrations, and therefore active magnetic bearings (AMBs) are often considered a good option for the main bearings, as the rotor then has no mechanical contact with other parts of the system but levitates on the magnetic forces. On the other hand, such systems can experience overloading or a sudden shutdown of the electrical system, whereupon the magnetic field becomes extinct, and as a result of rotor delevitation, mechanical contact occurs. To manage such nonstandard operations, AMB-systems require mechanical touchdown bearings with an oversized bore diameter. The need for touchdown bearings seems to be one of the barriers preventing greater adoption of AMB technology, because in the event of an uncontrolled touchdown, failure may occur, for example, in the bearing’s cage or balls, or in the rotor. This dissertation consists of two parts: First, touchdown bearing misalignment in the contact event is studied. It is found that misalignment increases the likelihood of a potentially damaging whirling motion of the rotor. A model for analysis of the stresses occurring in the rotor is proposed. In the studies of misalignment and stresses, a flexible rotor using a finite element approach is applied. Simplified models of cageless and caged bearings are used for the description of touchdown bearings. The results indicate that an increase in misalignment can have a direct influence on the bending and shear stresses occurring in the rotor during the contact event. Thus, it was concluded that analysis of stresses arising in the contact event is essential to guarantee appropriate system dimensioning for possible contact events with misaligned touchdown bearings. One of the conclusions drawn from the first part of the study is that knowledge of the forces affecting the balls and cage of the touchdown bearings can enable a more reliable estimation of the service life of the bearing. Therefore, the second part of the dissertation investigates the forces occurring in the cage and balls of touchdown bearings and introduces two detailed models of touchdown bearings in which all bearing parts are modelled as independent bodies. Two multibody-based two-dimensional models of touchdown bearings are introduced for dynamic analysis of the contact event. All parts of the bearings are modelled with geometrical surfaces, and the bodies interact with each other through elastic contact forces. To assist in identification of the forces affecting the balls and cage in the contact event, the first model describes a touchdown bearing without a cage, and the second model describes a touchdown bearing with a cage. The introduced models are compared with the simplified models used in the first part of the dissertation through parametric study. Damages to the rotor, cage and balls are some of the main reasons for failures of AMB-systems. The stresses in the rotor in the contact event are defined in this work. Furthermore, the forces affecting key bodies of the bearings, cage and balls can be studied using the models of touchdown bearings introduced in this dissertation. Knowledge obtained from the introduced models is valuable since it can enable an optimum structure for a rotor and touchdown bearings to be designed.

Three mechanical weed control techniques in spring cereals

Selostus: Kolme viljojen mekaanista rikkakasvintorjuntamentelmää

Effect of boric acid treatment on mechanical properties of laminated beech veneer lumber

Abstract

Influence of silvicultural regime on wood structure characteristics and mechanical properties of clear wood in Pinus sylvestris

Abstract

Development of Craniofacial Bone Defect Reconstruction Implant Based on Fibre-Reinforced Composite with Photopolymerisable Resin Systems. Experimental studies in vitro and in vivo.

Reconstruction of defects in the craniomaxillofacial (CMF) area has mainly been based on bone grafts or metallic fixing plates and screws. Particularly in the case of large calvarial and/or craniofacial defects caused by trauma, tumours or congenital malformations, there is a need for reliable reconstruction biomaterials, because bone grafts or metallic fixing systems do not completely fulfill the criteria for the best possible reconstruction methods in these complicated cases. In this series of studies, the usability of fibre-reinforced composite (FRC) was studied as a biostable, nonmetallic alternative material for reconstructing artificially created bone defects in frontal and calvarial areas of rabbits. The experimental part of this work describes the different stages of the product development process from the first in vitro tests with resin-impregnated fibrereinforced composites to the in vivo animal studies, in which this FRC was tested as an implant material for reconstructing different size bone defects in rabbit frontal and calvarial areas. In the first in vitro study, the FRC was polymerised in contact with bone or blood in the laboratory. The polymerised FRC samples were then incubated in water, which was analysed for residual monomer content by using high performance liquid chromatography (HPLC). It was found that this in vitro polymerisation in contact with bone and blood did not markedly increase the residual monomer leaching from the FRC. In the second in vitro study, different adhesive systems were tested in fixing the implant to bone surface. This was done to find an alternative implant fixing system to screws and pins. On the basis of this study, it was found that the surface of the calvarial bone needed both mechanical and chemical treatments before the resinimpregnated FRC could be properly fixed onto it. In three animal studies performed with rabbit frontal bone defects and critical size calvarial bone defect models, biological responses to the FRC implants were evaluated. On the basis of theseevaluations, it can be concluded that the FRC, based on E-glass (electrical glass) fibres forming a porous fibre veil enables the ingrowth of connective tissues to the inner structures of the material, as well as the bone formation and mineralization inside the fibre veil. Bone formation could be enhanced by using bioactive glass granules fixed to the FRC implants. FRC-implanted bone defects healed partly; no total healing of defects was achieved. Biological responses during the follow-up time, at a maximum of 12 weeks, to resin-impregnated composite implant seemed to depend on the polymerization time of the resin matrix of the FRC. Both of the studied resin systems used in the FRC were photopolymerised and the heat-induced postpolymerisation was used additionally.

Optimal Mechanical PulpingProcesses for Eucalyptus, Acacia and Birch

Tässä diplomityössä tutkittiin ja vertailtiin eukalyptuksen, akaasian ja koivun kemimekaanista kuiduttamista ja valkaisua. Yleensä näitä puulajeja käytetään sellun keittoon. Puulajit eroavat toisistaan kasvupaikan ja kuiturakenteen osalta. Eukalyptus ja akaasia ovat niin sanottuja trooppisia lehtipuita, kun taas koivu kasvaa pohjoisilla vyöhykkeillä. Koivulla on kookkaimmat kuidut ja akaasialla pienimmät kuidut. Myös näiden lajien putkilot eroavat toisistaan. Koivun putkilot ovat pitkiä ja kapeita, kun taas eukalyptuksen ja akaasian putkilot ovat lyhyitä ja leveitä. Prosessiksi valittiin kaksivaiheinen APMP-prosessi. Koeajot tehtiinKeskuslaboratorio Oy:ssä. Massoille asetettiin seuraavat tavoitteet: freeness 150-200 ml ja vaaleus 80 %ISO. Eukalyptukselle ja koivulle tehtiin kaksi erilaista impregnointisarjaa, mutta akaasialle vain yksi. Jauhatuksen viimeisessä vaiheessa kokeiltiin myös jauhinvalkaisua. Jauhatuksen energiankulutus oli korkea varsinkin eukalyptuksella ja akaasialla. Jotta energiankulutus saataisiin pienemmäksi, tulisi käyttää enemmän lipeää, mutta se johtaa alkalitummumiseen. Lopuksi massat valkaistiin laboratoriossa. Eukalyptus ja koivu pystyttiin valkaisemaan vaaleuteen 80 %ISO, mutta eukalyptuksen valkaisu vaati enemmän peroksidia kuin koivun valkaisu. Akaasian lähtövaaleus oli niin alhainen, ettei siinä päästy tavoitevaaleuteen. Eukalyptuksella on parempi valonsironta ja paremmat lujuusominaisuudet kuin koivulla. Kemimekaanista massaa voidaan käyttää hienopaperissa parantamassa jäykkyyttä, bulkkia ja valonsirontaa, mutta usein ongelmana on alhainen vaaleus ja huono vaaleuden pysyvyys. Kemimekaanista massaa voidaankäyttää missä tahansa mekaanisissa painopapereissa. Mekaanisissa painopapereissa kemimekaanisella lehtipuumassalla voidaan korvata mekaanista havupuumassaa. Akaasia on niin tummaa, ettei sitä voida käyttää korkeavaaleuksisiin papereihin. Eukalyptus ja koivu ovat vaaleampia ja helpompia valkaista kuin akaasia, mutta myös niillä on niin huono vaaleudenpysyvyys että käyttö hienopapereissa on rajoittunutta. Mekaanisille eukalyptus ja koivumassoille hienopaperia parempi käyttökohde on mekaaniset painopaperit, kuten MWC-paperi.

Aktiivisten magneettilaakereiden tilasäädön mallinnus ja simulointi

Aktiivisten magneettilaakereiden avulla on mahdollista kannatella ferromagneettisia kappaleita, kuten sähkökoneiden roottoreita, ilman fyysistä kontaktia. Magneettilaakerit tarjoavat monia etuja, kuten esimerkiksi kitkattomuuden, verrattuina perinteisiin mekaanisiin laakereihin. Nämä edut vielä korostuvat suurnopeuskäytöissä, jotka ovat magneettilaakereiden pääasiallisia käyttökohteita. Tässä työssä esitellään magneettilaakereihin liittyvät erusteoriat ja niiden sovellustavat. Tämän jälkeen tarkastellaanmagneettilaakereiden kanssa käytettäviä säätöratkaisuja ja esitetään niille soveltuvat viritysmenetelmät. Teorioiden pohjalta rakennetaan täydellinen magneettilaakerijärjestelmän simulointimalli säätöratkaisuineen ja suoritetaan järjestelmän toimintaa kuvaavia simulointeja. Simuloinneissa saadut tulokset pyritään vielä varmentamaan suorittamalla mittauksia koelaitteistolla ja vertaamalla saatuja tuloksia keskenään.

The Influence of Process Conditions on the Deresination Efficiency in Mechanical Pulp Washing

The aim of this thesis was to produce information for the estimation of the flow balance of wood resin in mechanical pulping and to demonstrate the possibilities for improving the efficiency of deresination in practice. It was observed that chemical changes in wood resin take place only during peroxide bleaching, a significant amount of water dispersed wood resin is retained in the pulp mat during dewatering and the amount of wood resin in the solid phase of the process filtrates is very small. On the basis of this information there exist three parameters related to behaviour of wood resin that determine the flow balance in the process: 1. The liberation of wood resin to the pulp water phase 2. Theretention of water dispersed wood resin in dewatering 3. The proportion of wood resin degraded in the peroxide bleaching The effect of different factors on these parameters was evaluated with the help of laboratory studies and a literature survey. Also, information related to the values of these parameters in existing processes was obtained in mill measurements. With the help of this information, it was possible to evaluate the deresination efficiency and the effect of different factors on this efficiency in a pulping plant that produced low-freeness mechanical pulp. This evaluation showed that the wood resin content of mechanical pulp can be significantly decreased if there exists, in the process, a peroxide bleaching and subsequent washing stage. In the case of an optimal process configuration, as high as a 85 percent deresination efficiency seems to be possible with a water usage level of 8 m3/o.d.t.