Comparison Between Damping Coefficients of Measured Perforated Micromechanical Test Structures and Compact Models

Measured damping coefficients of six different perforated micromechanical test structures are compared with damping coefficients given by published compact models. The motion of the perforated plates is almost translational, the surface shape is rectangular, and the perforation is uniform validating the assumptions made for compact models. In the structures, the perforation ratio varies from 24% - 59%. The study of the structure shows that the compressibility and inertia do not contribute to the damping at the frequencies used (130kHz - 220kHz). The damping coefficients given by all four compact models underestimate the measured damping coefficient by approximately 20%. The reasons for this underestimation are discussed by studying the various flow components in the models.Comment: Submitted on behalf of EDA Publishing Association (http://irevues.inist.fr/handle/2042/16838

Evaluation of constraint effects on the T0 temperature of miniature SE(N)T specimens

Abstract. The thesis explores the fracture toughness values derived using miniature SE(N)T specimens using the Master Curve method as described in the standard ASTM E1921. By comparing the results to previous experiments conducted on the ASTM A533B Class 1 pressure vessel steel designated JRQ, the effects of size and especially the constrain effect on fracture toughness are investigated. The experimental section consists of 12 a/W 0.5 and 11 a/W 0.2 crack depth SE(N)T tests. The effect of constraint on the T0 temperature is investigated by comparing the toughness values between the two crack depths. The CMOD and force are measured, and the area under the graph they form is analyzed to derive J-integral, KJc and the T0 temperature using the Master Curve method. The a/W 0.5 specimens produced a T0 temperature of -54 C which is on the brittle side for the reference material. Depending on the level of censorship the 0.2 a/W specimens had an uncensored T0 temperature of -113 C and a censored T0 temperature of -98 C. Both are tougher than the comparison values used. The difference in T0 temperature reflects a change in toughness which was 44 C between the specimen types. The constraint effect was evaluated with an Abaqus CAE FEM model from which Q-parameters were derived using the HRR field as a reference. The modelled difference between the specimen types was 29 C which is within the margin of error of the experimental results. The SE(N)T specimens were observed to be sensitive to constraint effects with respect to the crack depth. The effect of specimen size could not be evaluated due to the limited number of experiments. The reliability of the measurement results was estimated using a partial derivatives method and Sobol’s indices. The results were supplemented with microscopy and hardness analysis.Constraint-efektin vaikutusten arvio T0 lämpötilaan miniatyyri SE(N)T murtovetosauvoilla. Tiivistelmä. Tässä diplomityössä selvitetään miniatyyrikokoisten SE(N)T tyypin murtovetosauvojen sitkeysarvoja käyttäen ASTM E1921 standardissa kuvattua Master Curve -menetelmää. Työn JRQ-nimetystä ASTM A533B materiaaliaihiosta aikaisemmin teetettyjen kokeiden tuloksiin vertailemalla tutkitaan koon ja erityisesti constraint-efektin vaikutusta murtositkeystuloksiin. Kokeellinen osuus koostuu 12 a/W 0.5 ja 11 a/W 0.2 SE(N)T-murtovetosauvoista, joiden välillä verrataan constraint-vaikutusta T0 lämpötilaan. Mittausdatasta voiman ja CMOD lukemien välille sovitetaan käyrä, jota analysoimalla johdetaan J, KJc ja T0 lämpö Master Curve -menetelmällä. Syväsäröisen sauvan T0 lämpötilaksi saatiin -54 C, mikä on hauras kyseiselle materiaalille. Matalasäröisen sauvan T0 lämpötila on sensurointimäärän mukaan -113 C sensuroimattomalle sarjalle ja -98 C sensuroidulle sarjalle. Tulos on sitkeämpi kuin vertailuaineisto samalle materiaalille. Ero T0 lämpötilassa heijastaa sitkeyden muutosta, joka oli sauvatyyppien välillä 44 C. Constraint-ilmiön Q-parametri johdettiin Abacus CAE FEM -mallin ja HRR-kentän avulla, minkä tulosten perusteella constraint-vaikutuksen ero sauvatyyppien välillä oli 29 C. Ero mallin ja kokeiden välillä on virhemarginaalin sisällä ja sauvatyypin todetaan olevan herkkä constraint-muutokselle särönsyvyyden suhteen. Koon vaikutusta sitkeysarvojen tilastolliseen hajoamaan ei pystytty määrittämään pienen datamäärän vuoksi. Mittausten luotettavuutta arvioitiin osittaisderivointiin pohjautuvan menetelmän ja Sobolin indeksien kautta ja tuloksia täydennettiin mikroskopialla ja kovuusmittauksilla

System for measuring steel scrap volume using depth imaging

Abstract. Sustainability and green values are major themes in the world today. Companies across all fields are constantly implementing new technologies to reduce emissions and to limit the magnitude of global warming. The steel industry in general is one of the major producers of carbon dioxide emissions. The objective of this thesis was to develop a system to measure the volume of scrap metal being charged to an electric arc furnace. Obtaining the scrap volume would help the furnace operators in timing the charging of scrap baskets, thus avoiding the adverse effects resulting from early and late charging. The intention is to increase the energy efficiency of the process. The theory section of the thesis provides a short overview of the electric arc furnace process and a more detailed description of the charging process. Depth imaging technologies are then explored from a theoretical standpoint to provide the background for the selection and usage of imaging hardware. In this thesis, design science research methodology was utilized to develop the scrap volume measurement system, which consists of imaging hardware and developed software. The actual contribution of this thesis is the algorithm to extract the height of the scrap surface level from a 3-dimensional image of scrap baskets. The development process was iteratively carried out in a steel factory. The system performance was evaluated in a real-world scenario. It was established that the system was able to capture 3-dimensional data from scrap baskets and determine the scrap surface level height according to the algorithm. However, for some cases the image capturing did not perform as expected. These failure cases were a result of either steel dust obstructing the scene or the inability of the camera to capture data from unreflective material. Further research prospects were identified during conducting of the thesis. The failure cases could be addressed either programmatically, with new hardware technology, or a combination of both. Also, research could be conducted on the usage of the information provided by the system in actual charging events with the goal of optimizing charging timing

Analytic model for perforated squeezed-film dampers

The concept of a perforation cell to derive simple analytic models for perforated squeezed-film dampers is applied. The perforation cell models the cylindrical volume around a single perforation. An extended Reynolds equation is then used to model the damping due both to the gas flow in the air gap and in the perforations. The method is applied in a rectangular damper with 4...64 square holes to derive the damping coefficient analytically. 3D FEM simulations are used to verify the model. The damping predicted by the model is in good agreement with that obtained with 3D FEM simulations. Sinusoidal small-amplitude velocities are assumed, and micromechanical dimensions are considered with rare gas effects in the slip flow regime (Kn < 0.1)

Koneoppimisen mahdollisuuksia terästutkimuksessa

Tiivistelmä. Työssä tarkastellaan koneoppivien mallien tarjoamia uusia mahdollisuuksia terästutkimuksen näkökannalta. Teoriaosuudessa käydään läpi datan rooli ja sen käsittely koneoppivien mallien kannalta, sekä perusprosessi koneoppivan mallin koostamisen takana. Tekstin painotus on materiaalitekniikan asiantuntijan osuudessa mallien kehittämisessä terästutkimuksessa ja -teollisuudessa. Erityyppisten koneoppivien mallien avulla saavutettuja tuloksia havainnollistetaan kirjallisuuden esimerkkien kautta, jotka osoittavat niiden menestyksen mikrorakenteiden karakterisoinnissa, teräksen valmistuksen prosessiparametrien optimoinnissa ja uusien seostusten kehittämisessä. Tutkielma tarjoaa pohjan mallien kehitykselle yhteistyössä tietojenkäsittelytieteiden ja muiden asiantuntijoiden kanssa, osana modernia T&K-ympäristöä sekä olemassa olevia tietokantoja. Sen oppeja voidaan yleistää myös terästutkimuksen ulkopuolelle.Possibilities of machine learning in steel research. Abstract. This thesis investigates the new possibilities that machine learning offers from the perspective of steel research. In the theory section the role and modification of data is described in conjunction with the basics of compiling a machine learning model. The emphasis of the work is on the part that a materials subject matter expert plays in the development of a machine learning model for steel industry or research. The success of different machine learning methods is demonstrated through literary examples in microstructural characterization, process optimization and synthesis of new alloy compositions. The thesis offers the basics needed for model development as a part of a modern R&D environment including existing databases and experts from computer science and other relevant fields. The knowledge presented can be generalized beyond steel research

Numerical and Compact Modelling of Squeeze-Film Damping in RF MEMS Resonators

Oscillatory gas flow in squeeze-film dampers is studied at frequencies where the length of the acoustic wave is comparable with the damper dimensions. Damping and spring forces are calculated both numerically and analytically from the linearized 2D Navier-Stokes equations. In addition to the low frequency region of inertialess gas, where the use of the Reynolds equation is limited, the new model considers several additional phenomena. These are the inertia of the gas,the transition from isothermal to adiabatic conditions, and the gap resonances at frequencies where the acoustic wavelength is comparable to the gap height. Velocity and temperature slip conditions are considered to make the model valid in micromechanical structures where the gap heights are of the order of a micrometer. An approximate compact model is derived combining the low frequency model and the gap resonance model. The accuracy of the compact model is studied by comparing its response to the numerical results calculated with the finite element method. The agreement is very good in a wide frequency band when the ratio of the damper width and the gap height is greater than 10. The numerical study and the compact model are directly applicable in predicting the damping and the resonance frequency shift due to air in RF MEMS resonators having narrow air gap widths and operating at frequencies where the wavelengths become comparable to the damper dimensions

VR safety training for Fab Lab

Abstract. With advancements in both hardware and software, virtual reality has become more common in homes, offices and other workplaces. As with all new technologies, it is important to find uses that are best suited for VR. Education and training are the most common professional applications for VR. In this thesis we describe ways that VR has been utilized by others, and introduce an application developed by us to display the possibilities brought by VR. We developed an application to teach safe behaviour when using a laser cutter, to aid in the education of new users of a Fabrication Laboratory (Fab Lab). The application was built using Unity3D game engine for the Oculus Quest 2 VR headset, and was tested in an evaluation by staff at the University of Oulu Fab Lab. There were four test users in total, all of them with limited experience using VR. A member of our team was there to guide them in the use of the application. After the evaluation was complete, the participants answered a questionnaire containing multiple-choice and open questions. From the evaluation with the staff and questionnaire responses, it was concluded that the application was a mixed success with positive feedback but caused VR sickness in many. In addition, the evaluation resulted in suggestions for improvements from the users. We had planned to add other features, which were not possible to include due to the tight schedule. The application showed a lot of potential for future improvement such as including other machinery and features located in the Fab Lab such as 3D Printers and vinyl cutters for safety training.VR turvallisuuskoulutus Fab Lab-ympäristöön. Tiivistelmä. Tietokonelaitteistojen ja ohjelmistojen kehittyessä virtuaalitodellisuudesta on tullut tavallisempaa kodeissa, toimistoissa ja työpaikoilla. Uusien teknologioiden, kuten VR:n, ilmaantuessa on tärkeää löytää käyttökohteita, jotka parhaiten hyödyntävät kyseistä teknologiaa. Tässä työssä kerromme tavoista joilla muut ovat hyödyntäneet VR:ää, ja tuomme julki kehittämämme sovelluksen, esittääksemme asioita joita VR mahdollistaa. Kehitimme sovelluksen opettaaksemme turvallisia toimintatapoja laserleikkuria käytettäessä, helpottaaksemme uusien Fabrication Laboratoryn(Fab Lab) käyttäjiä. Sovellus on kehitetty Oculus Quest 2 -VR-laseille käyyttäen Unity3D pelimoottoria, ja sitä on testannut Fab Labin henkilökunta. Testikäyttäjiä oli neljä, ja heillä kaikilla oli hierman kokemusta VR:n käytöstä. Yksi ryhmämme jäsenistä oli mukana testaustilanteessa, opastamassa sovelluksen käyttöä. Käyttäjätestauksen jälkeen testaajat vastasivat kyselyyn jossa oli monivalinta- sekä avoimia kysymyksiä. Käyttäjätestauksesta ja kyselyn vastauksista tulkiten sovelluksen menestys oli keskinkertainen. Käyttäjät antoivat positiivista palautetta ja ehdotuksia sovelluksen kehittämiseen, mutta käytöstä aiheutui pahoinvointia useille. Tarkoituksenamme oli kehittää enemmän toiminnallisuutta, mutta rajoitteena oli tiukka aikataulu. Sovelluksella on paljon potentiaalia turvallisuusopetuksen laajentamiseksi, ja siihen voisi lisätä muita Fab Labissa sijaitsevia laitteita, kuten 3D-tulostimia ja vinyylileikkurin

Analyses of regulatory CD4(+)CD25(+)FOXP3(+) T cells and observations from peripheral T cell subpopulation markers during the development of type 1 diabetes in children

Our aim was to study whether the aberrant amount or function of regulatory T cells is related to the development of type 1 diabetes (T1D) in children. We also set out to investigate the balance of different T cell subtype markers during the T1D autoimmune process. Treg cells were quantified with flow cytometric assay, and the suppression capacity was analysed with a carboxyfluorescein succinimidyl ester (CFSE)-based T cell suppression assay in children in various phases of T1D disease process and in healthy autoantibody-negative control children. The mRNA expression of different T cell subpopulation markers was analysed with real-time qPCR method. The proportion and suppression capacity of regulatory T cells were similar in seroconverted children at an early stage of beta cell autoimmunity and also in children with T1D when compared to healthy and autoantibody-negative children. Significant differences were observed in the mRNA expression of different T cell subpopulation markers in prediabetic children with multiple (2) autoantibodies and in children with newly diagnosed T1D when compared to the control children. In conclusion, there were no quantitative or functional differences in regulatory T cells between the case and control groups in any phase of the autoimmune process. Decreased mRNA expression levels of T cell subtype markers were observed in children with multiple islet autoantibodies and in those with newly diagnosed T1D, probably reflecting an exhaustion of the immune system after the strong immune activation during the autoimmune process or a generally aberrant immune response related to the progression of the disease.Peer reviewe

Smoking in pregnancy, adolescent mental health and cognitive performance in young adult offspring: results from a matched sample within a Finnish cohort

$\textbf{Background:}$ The association between prenatal exposure to maternal cigarette smoking (PEMCS) and adult cognition is debated, including if there are differences according to sex. We aimed to determine if there are associations between PEMCS and cognition in early adulthood in men and women and examine if observed associations were mediated by adolescent mental health factors that are associated with cognition, namely psychotic-like experiences (PLEs), inattention and hyperactivity, and other externalizing behaviors. $\textbf{Methods:}$ Participants were 471 individuals drawn from the general population-based Northern Finland 1986 Birth Cohort (NFBC 1986) followed up from pregnancy and birth to early adulthood; individuals with PEMCS were matched with those without PEMCS by socioeconomic and demographic factors. Cognitive performance in adulthood was assessed with a range of tests and their association with PEMCS was measured by sex using hierarchical linear regression, unadjusted and then controlling for potential confounders, mediators and moderators, including adolescent mental health factors. $\textbf{Results:}$ There were no associations between PEMCS and cognitive scores in females. In males, there were associations with vocabulary (beta = -0.444, 95% CI: -0.783, -0.104) and matrix reasoning (beta = -0.379, 95% CI: -0.711, -0.047). $\textbf{Conclusions:}$ While associations between PEMCS and cognition were limited, observed findings with measures of general intelligence in males contribute to suggestions of differences in response to PEMCS by sex. Furthermore, observed associations may be partly mediated by earlier inattention and hyperactivity. Findings add support to efforts aimed to eliminate smoking in pregnancy.The Northern Finland Birth Cohort 1986 is funded by the University of Oulu, University Hospital of Oulu, Academy of Finland, Sigrid Juselius Foundation, European Commission (EURO-BLCS, Framework 5 award QLG1-CT-2000- 01643), and NIH/NIMH (5R01MH63706:02). Cambridge Cognition Ltd. provided support in the form of salaries for author Jennifer H. Barnett