Valusenkan liukusulkimen säätöpiirin optimaalinen viritys

Tiivistelmä. Työn tavoitteena oli tutkia Outokummun Tornion tehtaan sulaton 2-linjan liukusulkimen säädön kehityspotentiaalia välialtaan painovaihtelujen minimoimiseksi. Välialtaan pienemmällä painohajonnalla haluttiin tehostaa kuonasulkeumien poistoa välialtaassa. Liukusulkimen säädön kehityksen yhteydessä tutkittiin myös mahdollisuutta vähentää liukusulkimen liikekertoja kulumisen vähentämiseksi. Tämän lisäksi tarkasteltiin muita mahdollisia välialtaan painovaihteluihin vaikuttavia tekijöitä. Työn alussa käytiin läpi terässulaton 2 linjan toimintaa ja tarkempaan tarkasteluun otettiin senkka-aseman, välialtaan ja liukusulkimen toiminta. Työssä tarkasteltiin aiempia samaan aihepiiriin liittyviä tutkimuksia ja niissä tehtyjä havaintoja, joista saatiin apua tässä työssä esiteltyihin parannusehdotuksiin. Työn teoriaosuudessa käytiin läpi mallinnusta, yleistä säätöpiireihin liittyvää teoriaa ja tässä työssä käytetyn Smith-prediktorin toimintaa. Kokeellisessa osuudessa tehtaalta saatua prosessidataa analysoitiin, minkä avulla luotiin kuva olemassa olevan prosessin käyttäytymisestä ja siihen liittyvän automaatiojärjestelmän toiminnasta. Tämän pohjalta kehitettiin useampi simulointimalli ja vaihtoehtoinen säätöratkaisu käyttäen Smith-prediktoria välialtaan painon ohjauksessa. Luoduilla simulointimalleilla simuloitiin ensisijaisesti välialtaan painoa, mutta myös liukusulkimen liikkeitä. Simulointien perusteella vaihtoehtoisella säädinratkaisulla saataisiin vähennettyä välialtaan painovaihteluja. Liukusulkimen liikekertoja saatiin simuloinneissa vähennettyä kasvattamalla sen minimiliikettä ilman, että välialtaan painovaihtelu olisi kasvanut. Liukusulkimen toiminnasta kuitenkin havaittiin, että sen nykyinen liike ei vastannut säätimen asettamia asetusarvoja halutulla tavalla, joten sen mekaaninen toimivuus on syytä varmistaa ennen mahdollisia muutoksia automaatiojärjestelmään. Simulointien osalta tulokset ovat suuntaa antavia ja prosessikokeisiin ei työssä ollut mahdollisuutta tulosten todentamiseksi.Optimal tuning of the ladle slide gate control system. Abstract. In this thesis, the aim was to study development potential of the slide gate control in order to minimize tundish weight variations at Outokumpu steel factory in Tornio. With smaller tundish weight variation,the desire was to improve removal of slag occlusions in the tundish. Possibility to reduce slide gate movements was also studied to reduce slide gate wear. In addition, other possible factors affecting tundish weight variations were studied. First the smelter production line 2 manufacturing process was introduced and then ladle station, tundish and slide gate operations were more closely looked at. Previous studies and their findings about the subject were examined which helped in this thesis when making suggestions for the improvements. Theory about modelling and control systems and how they link to this study were presented on the theory part of this thesis as well as the working principle of Smith predictor was explained. Process data was acquired from the factory for analysis which helped studying the behavior and the automation system of the process. This served as a basis for creating multiple simulation models and an alternative control system using Smith predictor to control tundish weight. Simulation models were used primarily to simulate tundish weight,but they were also used to simulate movement of the slide gate. Based on simulation results,the alternative control system provided decrease in tundish weight variation. Reduction of slide gate movements was achieved by increasing minimum movement of the slide gate without increasing tundish weight variation. It was also noticed that slide gate movement was not corresponding to the values set by the controller in the current system, which would require attention before any other implementations to the automation system. The results concerning simulations in this thesis are only indicative and there was no opportunity for process experiments to confirm these results

Structural and transport properties of GaAs/delta<Mn>/GaAs/InxGa1-xAs/GaAs quantum wells

We report results of investigations of structural and transport properties of GaAs/Ga(1-x)In(x)As/GaAs quantum wells (QWs) having a 0.5-1.8 ML thick Mn layer, separated from the QW by a 3 nm thick spacer. The structure has hole mobility of about 2000 cm2/(V*s) being by several orders of magnitude higher than in known ferromagnetic two-dimensional structures. The analysis of the electro-physical properties of these systems is based on detailed study of their structure by means of high-resolution X-ray diffractometry and glancing-incidence reflection, which allow us to restore the depth profiles of structural characteristics of the QWs and thin Mn containing layers. These investigations show absence of Mn atoms inside the QWs. The quality of the structures was also characterized by photoluminescence spectra from the QWs. Transport properties reveal features inherent to ferromagnetic systems: a specific maximum in the temperature dependence of the resistance and the anomalous Hall effect (AHE) observed in samples with both "metallic" and activated types of conductivity up to ~100 K. AHE is most pronounced in the temperature range where the resistance maximum is observed, and decreases with decreasing temperature. The results are discussed in terms of interaction of 2D-holes and magnetic Mn ions in presence of large-scale potential fluctuations related to random distribution of Mn atoms. The AHE values are compared with calculations taking into account its "intrinsic" mechanism in ferromagnetic systems.Comment: 15 pages, 9 figure

Fractal space-times under the microscope: A Renormalization Group view on Monte Carlo data

The emergence of fractal features in the microscopic structure of space-time is a common theme in many approaches to quantum gravity. In this work we carry out a detailed renormalization group study of the spectral dimension $d_s$ and walk dimension $d_w$ associated with the effective space-times of asymptotically safe Quantum Einstein Gravity (QEG). We discover three scaling regimes where these generalized dimensions are approximately constant for an extended range of length scales: a classical regime where $d_s = d, d_w = 2$, a semi-classical regime where $d_s = 2d/(2+d), d_w = 2+d$, and the UV-fixed point regime where $d_s = d/2, d_w = 4$. On the length scales covered by three-dimensional Monte Carlo simulations, the resulting spectral dimension is shown to be in very good agreement with the data. This comparison also provides a natural explanation for the apparent puzzle between the short distance behavior of the spectral dimension reported from Causal Dynamical Triangulations (CDT), Euclidean Dynamical Triangulations (EDT), and Asymptotic Safety.Comment: 26 pages, 6 figure

Gas phase synthesis of non-bundled, small diameter single-walled carbon nanotubes with near-armchair chiralities

We present a floating catalyst synthesis route for individual, i.e., non-bundled, small diameter single-walled carbon nanotubes (SWCNTs) with a narrow chiral angle distribution peaking at high chiralities near the armchair species. An ex situ spark discharge generator was used to form iron particles with geometric number mean diameters of 3–4 nm and fed into a laminar flow chemical vapour deposition reactor for the continuous synthesis of long and high-quality SWCNTs from ambient pressure carbon monoxide. The intensity ratio of G/D peaks in Raman spectra up to 48 and mean tube lengths up to 4 μm were observed. The chiral distributions, as directly determined by electron diffraction in the transmission electron microscope, clustered around the (n,m) indices (7,6), (8,6), (8,7), and (9,6), with up to 70% of tubes having chiral angles over 20°. The mean diameter of SWCNTs was reduced from 1.10 to 1.04 nm by decreasing the growth temperature from 880 to 750 °C, which simultaneously increased the fraction of semiconducting tubes from 67% to 80%. Limiting the nanotube gas phase number concentration to ∼10 exp 5 cm exp −3 prevented nanotube bundle formation that is due to collisions induced by Brownian diffusion. Up to 80% of 500 as-deposited tubes observed by atomic force and transmission electron microscopy were individual. Transparent conducting films deposited from these SWCNTs exhibited record low sheet resistances of 63 Ω/□ at 90% transparency for 550 nm light.Peer reviewe

Detection of a low-grade enteroviral infection in the islets of Langerhans of living patients newly diagnosed with type 1 diabetes

Journal ArticleThis is an author-created, uncopyedited electronic version of an article accepted for publication in Diabetes. The American Diabetes Association (ADA), publisher of Diabetes, is not responsible for any errors or omissions in this version of the manuscript or any version derived from it by third parties. The definitive publisher-authenticated version is available in Diabetes, May 2015, vol. 64, no. 5 pp. 1682-1687 in print and online at http://diabetes.diabetesjournals.org/content/64/5/1682.abstractThe Diabetes Virus Detection study (DiViD) is the first to examine fresh pancreatic tissue at the diagnosis of type 1 diabetes for the presence of viruses. Minimal pancreatic tail resection was performed 3-9 weeks after onset of type 1 diabetes in six adult patients (age 24-35 years). The presence of enteroviral capsid protein 1 (VP1) and the expression of class I HLA were investigated by immunohistochemistry. Enterovirus RNA was analyzed from isolated pancreatic islets and from fresh-frozen whole pancreatic tissue using PCR and sequencing. Nondiabetic organ donors served as controls. VP1 was detected in the islets of all type 1 diabetic patients (two of nine controls). Hyperexpression of class I HLA molecules was found in the islets of all patients (one of nine controls). Enterovirus-specific RNA sequences were detected in four of six patients (zero of six controls). The results were confirmed in various laboratories. Only 1.7% of the islets contained VP1(+) cells, and the amount of enterovirus RNA was low. The results provide evidence for the presence of enterovirus in pancreatic islets of type 1 diabetic patients, which is consistent with the possibility that a low-grade enteroviral infection in the pancreatic islets contributes to disease progression in humans.Academy of FinlandSouth-Eastern Norway Regional HealthAuthorityNovo Nordisk FoundationPEVNET (Persistent Virus Infection in Diabetes Network) Study GroupEuropean Union’s Seventh Framework ProgrammeSwedish Medical Research CouncilDiabetes Wellness FoundationJDR

Flavour physics from an approximate U(2)^3 symmetry

The quark sector of the Standard Model exhibits an approximate U(2)^3 flavour symmetry. This symmetry, broken in specific directions dictated by minimality, can explain the success of the Cabibbo-Kobayashi-Maskawa picture of flavour mixing and CP violation, confirmed by the data so far, while allowing for observable deviations from it, as expected in most models of ElectroWeak Symmetry Breaking. Building on previous work in the specific context of supersymmetry, we analyze the expected effects and we quantify the current bounds in a general Effective Field Theory framework. As a further relevant example we then show how the U(2)^3 symmetry and its breaking can be implemented in a generic composite Higgs model and we make a first analysis of its peculiar consequences. We also discuss how some partial extension of U(2)^3 to the lepton sector can arise, both in general and in composite Higgs models. An optimistic though conceivable interpretation of the considerations developed in this paper gives reasons to think that new physics searches in the flavour sector may be about to explore an interesting realm of phenomena.Comment: 29 pages, 5 figure

Self-completeness and spontaneous dimensional reduction

A viable quantum theory of gravity is one of the biggest challenges facing physicists. We discuss the confluence of two highly expected features which might be instrumental in the quest of a finite and renormalizable quantum gravity -- spontaneous dimensional reduction and self-completeness. The former suggests the spacetime background at the Planck scale may be effectively two-dimensional, while the latter implies a condition of maximal compression of matter by the formation of an event horizon for Planckian scattering. We generalize such a result to an arbitrary number of dimensions, and show that gravity in higher than four dimensions remains self-complete, but in lower dimensions it is not. In such a way we established an "exclusive disjunction" or "exclusive or" (XOR) between the occurrence of self-completeness and dimensional reduction, with the goal of actually reducing the unknowns for the scenario of the physics at the Planck scale. Potential phenomenological implications of this result are considered by studying the case of a two-dimensional dilaton gravity model resulting from dimensional reduction of Einstein gravity.Comment: 12 pages, 3 figures; v3: final version in press on Eur. Phys. J. Plu