The Optimization of Flotation Process Parameters in the Deinking Plant

Tämän diplomityön tavoitteena oli sekundäärisen esiflotaation optimointi Stora Enso Sachsen GmbH:n tehtaalla. Optimoinnin muuttujana käytettiin vaahdon määrää ja optimointiparametreinä ISO-vaaleutta, saantoja sekä tuhkapitoisuutta. Lisäksi tutkittiin flotaatiosakeuden vaikutusta myös muihin tehtaan flotaatioprosesseihin. Kirjallisuusosassa tarkasteltiin flotaatiotapahtumaa, poistettavien partikkeleiden ja ilmakuplien kontaktia, vaahdon muodostumista sekä tärkeimpiä käytössä olevia siistausflotaattoreiden laiteratkaisuja. Kokeellisessa osassa tutkittiin flotaatiosakeuden pienetämisen vaikutuksia tehtaan flotaatioprosesseihin tuhkapitoisuuden, ISO-vaaleuden, valon sironta- ja valon absorpiokerrointen kannalta. Sekundäärisen esiflotaation optimonti suoritettiin muuttamalla vaahdon määrää kolmella erilaisella injektorin koolla, (8 mm, 10 mm ja 13 mm), joista keskimmäinen kasvattaa 30 % massan tilavuusvirtaa ilmapitoisuuden muodossa. Optimonnin tarkoituksena oli kasvattaa hyväksytyn massajakeen ISO-vaaleutta, sekä kasvattaa kuitu- ja kokonaissaantoa sekundäärisessä esiflotaatiossa. Flotaatiosakeuden pienentämisellä oli edullisia vaikutuksia ISO-vaaleuteen ja valon sirontakertoimeen kussakin flotaatiossa. Tuhkapitoisuus pieneni sekundäärisissä flotaatioissa enemmän sakeuden ollessa pienempi, kun taas primäärisissä flotaatiossa vaikutus oli päinvastainen. Valon absorptiokerroin parani jälkiflotaatioissa alhaisemmalla sakeudella, kun taas esiflotaatioissa vaikutus oli päinvastainen. Sekundäärisen esiflotaation optimoinnin tuloksena oli lähes 5 % parempi ISO-vaaleus hyväksytyssä massajakeessa. Kokonaissaanto parani optimoinnin myötä 5 % ja kuitusaanto 2 %. Saantojen nousu tuottaa vuosittaisia säästöjä siistauslaitoksen tuotantokapasiteetin noustessa 0,5 %. Tämän lisäksi sekundäärisessä esiflotaatiossa rejektoituvan massavirran pienentyminen tuottaa lisäsäästöjä tehtaan voimalaitoksella.

Flash Memory Cells Reliability Parameters Investigation

The present work is a part of the large project with purpose to qualify the Flash memory for automotive application using a standardized test and measurement flow. High memory reliability and data retention are the most critical parameters in this application. The current work covers the functional tests and data retention test. The purpose of the data retention test is to obtain the data retention parameters of the designed memory, i.e. the maximum time of information storage at specified conditions without critical charge leakage. For this purpose the charge leakage from the cells, which results in decrease of cells threshold voltage, was measured after a long-time hightemperature treatment at several temperatures. The amount of lost charge for each temperature was used to calculate the Arrhenius constant and activation energy for the discharge process. With this data, the discharge of the cells at different temperatures during long time can be predicted and the probability of data loss after years can be calculated. The memory chips, investigated in this work, were 0.035 μm CMOS Flash memory testchips, designed for further use in the Systems-on-Chips for automotive electronics.

Epidemiological studies of childhood and adolescence headache

The main purpose of this study was to examine the changes in the prevalence, incidence, and characteristics of headache in childhood and adolescence. In addition, the predictors of the change in the occurrence of childhood headache and the association between adolescent headache and behavior were studied. The occurrence and characteristics of headache were investigated as part of a prospective follow-up study, where 6-year-old children and their families (n=1132) were followed to the age of 12-years (n=1126). The study design entailed both a cohort and case-control group. The incidence of headache and the association between headache and behavior were studied in another cohort, consisting of 11-year-old twins (n=5393), who were followed to the age of 17 (n=4159). The prevalence rates of headache increased during the follow-up, especially in boys whose mothers suffered from frequent headache. The incidence rates of frequent headache changed the most in girls between ages of 11 and 14. Early-onset migraine and tension-type headache were equal predictors of migraine at age 12. The age-related changes observed in pain localization, concurrent symptoms and triggers were considerable. Headache frequency was significantly associated with externalizing and internalizing problem behaviors and adaptive behaviors as rated by parents, but only with externalizing problem behaviors as rated by teachers. Headache both in children and adolescents is characterized by its changing nature. Its prevention and treatment should take familial, environmental and psychosocial aspects into account.

Energy efficiency parameters in variable speed drives

The main purpose of this thesis is to measure and evaluate how accurately the current energy saving calculation in ABB’s new variable speed drive ACS850 works. The main topic of this thesis is energy-efficiency parameters. At the beginning of this thesis centrifugal pump, squirrel cage motor and variable speed drive, including some equations related to them, are being introduced. Also methods of throttling control and variable speed drive control of centrifugal pumps are being introduced. These subjects are introduced because the energy saving calculation in ACS850 is related to the centrifugal pumps usually driven by squirrel cage motors. The theory also includes short section about specific energy of pumping. Before measurements the current energy saving calculation of ACS850 is being introduced and analyzed. The measurements part includes introduction of measuring equipment, measurement results, summary and analysis of the measurements. At the end of this thesis a proposal for an improvement to the current energy saving calculation is being introduced and few proposals are made for new energy-efficiency parameters, which could be added to variable speed drives. At the end are also thoughts

On the effects of welding parameters on weld quality of plasma arc keyhole welding of structural steels

The possibility and the usefulness of applying plasma keyhole welding to structural steels with different compositions and material thicknesses, and in various welding positions has been examinated. Single pass butt welding with I groove in flat, horizontal vertical and vertical positions and root welding with V , Y and U grooves of thick plate material in flat position have been studied and the welds with high quality has been obtained. The technological conditions for successful welding are presented. The single and interactive effects of welding parameters on weld quality, especially on surface weld defects, geometrical form errors, internal defects and mechanical properties (strength, ductility, impact toughness, hardness and bendability) of weld joint, are presented. Welding parameter combinations providing the best quality welds are also presented.

The effects of real time control of welding parameters on weld quality in plasma arc keyhole welding

Joints intended for welding frequently show variations in geometry and position, for which it is unfortunately not possible to apply a single set of operating parameters to ensure constant quality. The cause of this difficulty lies in a number of factors, including inaccurate joint preparation and joint fit up, tack welds, as well as thermal distortion of the workpiece. In plasma arc keyhole welding of butt joints, deviations in the gap width may cause weld defects such as an incomplete weld bead, excessive penetration and burn through. Manual adjustment of welding parameters to compensate for variations in the gap width is very difficult, and unsatisfactory weld quality is often obtained. In this study a control system for plasma arc keyhole welding has been developed and used to study the effects of the real time control of welding parameters on gap tolerance during welding of austenitic stainless steel AISI 304L. The welding tests demonstrated the beneficial effect of real time control on weld quality. Compared with welding using constant parameters, the maximum tolerable gap width with an acceptable weld quality was 47% higher when using the real time controlled parameters for a plate thickness of 5 mm. In addition, burn through occurred with significantly larger gap widths when parameters were controlled in real time. Increased gap tolerance enables joints to be prepared and fit up less accurately, saving time and preparation costs for welding. In addition to the control system, a novel technique for back face monitoring is described in this study. The test results showed that the technique could be successfully applied for penetration monitoring when welding non magnetic materials. The results also imply that it is possible to measure the dimensions of the plasma efflux or weld root, and use this information in a feedback control system and, thus, maintain the required weld quality.

Ecological and Epidemiological Analyses of Multiple Sclerosis Relapse Rate

The underlying cause of many human autoimmune diseases is unknown, but several environmental factors are implicated in triggering the self-destructive immune reactions. Multiple Sclerosis (MS) is a chronic autoimmune disease of the central nervous system, potentially leading to persistent neurological deterioration. The cause of MS is not known, and apart from immunomodulatory treatments there is no cure. In the early phase of the disease, relapsing-remitting MS (RR-MS) is characterized by unpredictable exacerbations of the neurological symptoms called relapses, which can occur at different intervals ranging from 4 weeks to several years. Microbial infections are known to be able to trigger MS relapses, and the patients are instructed to avoid all factors that might increase the risk of infections and to properly use antibiotics as well as to take care of dental hygiene. Among those environmental factors which are known to increase susceptibility to infections, high ambient air inhalable particulate matter levels affect all people within a geographical region. During the period of interest in this thesis, the occurrence of MS relapses could be effectively reduced by injections of interferon, which has immunomodulatory and antiviral properties. In this thesis, ecological and epidemiological analyses were used to study the possible connection between MS relapse occurrence, population level viral infections and air quality factors, as well as the effects of interferon medication. Hospital archive data were collected retrospectively from 1986-2001, a period in time ranging from when interferon medication first became available until just before other disease-modifying MS therapies arrived on the market. The grouped data were studied with logistic regression and intervention analysis, and individual patient data with survival analysis. Interferons proved to be effective in the treatment of MS in this observational study, as the amount of MS exacerbations was lower during interferon use as compared to the time before interferon treatment. A statistically significant temporal relationship between MS relapses and inhalable particular matter (PM₁₀) concentrations was found in this study, which implies that MS patients are affected by the exposure to PM₁₀. Interferon probably protected against the effect of PM₁₀, because a significant increase in the risk of exacerbations was only observed in MS patients without interferon medication following environmental exposure to population level specific viral infections and PM₁₀. Apart from being antiviral, interferon could thus also attenuate the enhancement of immune reactions caused by ambient air PM₁₀. The retrospective approach utilizing carefully constructed hospital records proved to be an economical and reliable source of MS disease information for statistical analyses.

Field Weakening, Parameters and Operation Range of the Permanent Magnet Traction Motors

The main focus of this thesis is to define the field weakening point of permanent magnet synchronous machine with embedded magnets in traction applications. Along with the thesis a modelling program is made to help the designer to define the field weakening point in practical applications. The thesis utilizes the equations based on the current angle. These equations can be derived from the vector diagram of permanent magnet synchronous machine. The design parameters of the machine are: The maximum rotational speed, saliency ratio, maximum induced voltage and characteristic current. The main result of the thesis is finding out the rated rotational speed, from which the field weakening starts. The action of the machine is estimated at a wide speed range and the changes of machine parameters are examined.

Neurobiology of pathological gambling. Brain imaging and epidemiological studies

Pathological gambling, a form of behavioral addiction, refers to maladaptive, compulsive gambling behavior severely interfering with an individual’s normal life. The prevalence of pathological gambling has been estimated to be 1–2% in western societies. The reward deficiency hypothesis of addiction assumes that individuals that have, or are prone, to addictions have blunted mesolimbic dopamine reward signaling, which leads to compulsive reward seeking in an attempt to compensate for the malfunctioning brain reward network. In this research project, the effects of gambling were measured using brain [11C] raclopride PET during slot machine gambling and possible brain structural changes associated with pathological gambling using MRI. The subjects included pathological gamblers and healthy volunteers. In addition, impulse control disorders associated with Parkinson’s disease were investigated by using brain [18F]fluorodopa PET and conducting an epidemiological survey. The results demonstrate mesolimbic dopamine release during gambling in both pathological gamblers and healthy volunteers. Striatal dopamine was released irrespective of the gambling outcome, whether the subjects won or not. There was no difference in gambling induced dopamine release between pathological gamblers and control subjects, although the magnitude of the dopamine release correlated with gambling related symptom severity in pathological gamblers. The results also show that pathological gambling is associated with extensive abnormality of brain white matter integrity, as measured with diffusion tensor imaging, similar to substance-addictions. In Parkinson’s disease patients with impulse control disorders, enhanced brain [18F] fluorodopa uptake in the medial orbitofrontal cortex was observed, indicating increased presynaptic monoamine function in this region, which is known to influence signaling in the mesolimbic system and reward processing. Finally, a large epidemiological survey in Finnish Parkinson’s disease patients showed that compulsive behaviors are very common in Parkinson disease and they are strongly associated with depression. These findings demonstrate the role of dopamine in pathological gambling, without support for the concept of reward deficiency syndrome.

Identification of research trends in the field of separation processes. Application of epidemiological model, citation analysis, text mining, and technical analysis of the financial markets

Choice of industrial development options and the relevant allocation of the research funds become more and more difficult because of the increasing R&D costs and pressure for shorter development period. Forecast of the research progress is based on the analysis of the publications activity in the field of interest as well as on the dynamics of its change. Moreover, allocation of funds is hindered by exponential growth in the number of publications and patents. Thematic clusters become more and more difficult to identify, and their evolution hard to follow. The existing approaches of research field structuring and identification of its development are very limited. They do not identify the thematic clusters with adequate precision while the identified trends are often ambiguous. Therefore, there is a clear need to develop methods and tools, which are able to identify developing fields of research. The main objective of this Thesis is to develop tools and methods helping in the identification of the promising research topics in the field of separation processes. Two structuring methods as well as three approaches for identification of the development trends have been proposed. The proposed methods have been applied to the analysis of the research on distillation and filtration. The results show that the developed methods are universal and could be used to study of the various fields of research. The identified thematic clusters and the forecasted trends of their development have been confirmed in almost all tested cases. It proves the universality of the proposed methods. The results allow for identification of the fast-growing scientific fields as well as the topics characterized by stagnant or diminishing research activity.

Numerical Simulation of Stochastic Di erential Equations

Stochastic differential equation (SDE) is a differential equation in which some of the terms and its solution are stochastic processes. SDEs play a central role in modeling physical systems like finance, Biology, Engineering, to mention some. In modeling process, the computation of the trajectories (sample paths) of solutions to SDEs is very important. However, the exact solution to a SDE is generally difficult to obtain due to non-differentiability character of realizations of the Brownian motion. There exist approximation methods of solutions of SDE. The solutions will be continuous stochastic processes that represent diffusive dynamics, a common modeling assumption for financial, Biology, physical, environmental systems. This Masters' thesis is an introduction and survey of numerical solution methods for stochastic differential equations. Standard numerical methods, local linearization methods and filtering methods are well described. We compute the root mean square errors for each method from which we propose a better numerical scheme. Stochastic differential equations can be formulated from a given ordinary differential equations. In this thesis, we describe two kind of formulations: parametric and non-parametric techniques. The formulation is based on epidemiological SEIR model. This methods have a tendency of increasing parameters in the constructed SDEs, hence, it requires more data. We compare the two techniques numerically.