Influence Of AirContent On Board Properties

Työn tarkoitus oli testata kartonkikoneen lyhyen kierron ilmapitoisuuden merkitystä kartongin ominaisuuksiin. Aluksi työssä selvitettiin ilmapitoisuuden alkutilanne käyttäen kompressioilmiöön perustuvaa ilmapitoisuusmittaria. Sen jälkeen tehtiin kokeita käyttäen POMp-pumppua sekä vaahdonestoainetta. Tarkoituksena oli luoda yhteys prosessin ilmapitoisuuden ja lopputuotteen ominaisuuksien välille. POMp-kokeissa tutkittiin keskipakopumppauksen vaikutusta massan ilmapitoisuuteen. Tuloksista nähdään, että pintakerroksen ilmapitoisuus oli suurempi kuin taustakerroksen, mikä selittyy POMp-pumpun sijainnilla taustakerroksen lyhyessä kierrossa. Vaahdonestoainekokeissa saatiin myös vaikutuksia massan ilmapitoisuuteen. Vaahdonestoaineen lisäyksen jälkeen runkokerroksenilmapitoisuus laski, kun samanaikaisesti pinta- ja taustakerroksen sekä rejektisysteemin ilmapitoisuudet nousivat. Ilmapitoisuuden käytöksen syyksi paljastui lyhyen kierron yhteinen vesikierto ja nykyisille tuotantomäärille alimitoitettu ilmanpoistokapasiteetti. Vaahdonestoaineen lisäyksen jälkeen vedenpoisto parani ja ensimmäisillä kolmella runkokerroksen foililaatikolla havaittiin poistuvan veden virtausten kasvaneen. Samaan aikaan runkokerroksen viiraosan lopulla poistuvan veden virtaukset pienenivät. Kartongin ominaisuuksissa ei havaittu kuitenkaan eroa, vaikka vedenpoisto parani viiraosalla selvästi. Vaahdonestoainekokeiden aikana oli myös tavallista enemmän ajettavuusongelmia, kuten ratakatkoja. Prosessissa esiintyneitä ongelmia ja niihin reagoivia muutosehdotuksia esitellään myös. Vaikein ongelma oli ilman muodostuminen runkokerroksen lyhyessä kierrossa. Ratkaisu voisi koostua isommasta keskikerroksenvesilukkosäiliöstä ja runkokerroksen lyhyen kierron puhdistusveden uudelleen kohdentamisesta. Voisi myös olla hyödyllistä yrittää ilmanpoistoa kemikaalien avulla kiertoveden varastosäiliössä.

Ruostumattoman teräksen TIG-hitsauksen hitsausnopeuden lisääminen

Diplomityön tavoitteena oli ruostumattoman teräksen koneellisen TIG-hitsauksen hitsausnopeuden lisääminen. Työssä tutkittiin suojakaasun koostumuksen vaikutusta hitsausnopeuteen sekä kahta uudehkoa prosessivariaatiota. Tutkitut prosessit olivat TIG-suurtaajuuspulssihitsaus sekä kaksoiskaasu-TIG-hitsaus. Kirjallisessa osassa perehdyttiin TIG-hitsauksen prosessiparametreihin ja -variaatioihin. Kokeellisessa osassa suoritettiin koehitsauksia hitsausnopeuksien selvittämiseksi. Tavoitteena oli tunkeuman kasvattaminen, mikä mahdollistaa hitsausnopeuden noston läpihitsattaessa. Suojakaasuina käytettiin sekä argonpohjaisia että heliumpohjaisia kaasuja, joihin oli lisätty vetyä. Vedyn avulla hitsausnopeus lisääntyi nykykäytäntöä suuremmillakin pitoisuuksilla. Uutena ilmiönä TIG-hitsauksessa havaittiin keyholen eli lävistysreiän syntyminen korkeita vetypitoisuuksia heliumpohjaisessa suojakaasussa käytettäessä. Keyhole oli kuitenkin erittäin epävakaa, joten jatkotutkimuksien tehtäväksi jää selvittää tarkemmin tämän ilmiön vaikutus. Tutkittuihin prosessivariaatioihin todettiin liittyvän useita laiteteknisiä ongelmia. Hitsausnopeuden suhteen tulokset jäivät vaatimattomiksi. Lähinnä keyholen aukaisemisessa ja aukipitämisessä menetelmistä havaittu hyöty antaa selvän aiheen jatkotutkimuksille.

Potential and Challenges of Analog Reconfigurable Computation in Modern and Future CMOS

In this work, the feasibility of the floating-gate technology in analog computing platforms in a scaled down general-purpose CMOS technology is considered. When the technology is scaled down the performance of analog circuits tends to get worse because the process parameters are optimized for digital transistors and the scaling involves the reduction of supply voltages. Generally, the challenge in analog circuit design is that all salient design metrics such as power, area, bandwidth and accuracy are interrelated. Furthermore, poor flexibility, i.e. lack of reconfigurability, the reuse of IP etc., can be considered the most severe weakness of analog hardware. On this account, digital calibration schemes are often required for improved performance or yield enhancement, whereas high flexibility/reconfigurability can not be easily achieved. Here, it is discussed whether it is possible to work around these obstacles by using floating-gate transistors (FGTs), and analyze problems associated with the practical implementation. FGT technology is attractive because it is electrically programmable and also features a charge-based built-in non-volatile memory. Apart from being ideal for canceling the circuit non-idealities due to process variations, the FGTs can also be used as computational or adaptive elements in analog circuits. The nominal gate oxide thickness in the deep sub-micron (DSM) processes is too thin to support robust charge retention and consequently the FGT becomes leaky. In principle, non-leaky FGTs can be implemented in a scaled down process without any special masks by using “double”-oxide transistors intended for providing devices that operate with higher supply voltages than general purpose devices. However, in practice the technology scaling poses several challenges which are addressed in this thesis. To provide a sufficiently wide-ranging survey, six prototype chips with varying complexity were implemented in four different DSM process nodes and investigated from this perspective. The focus is on non-leaky FGTs, but the presented autozeroing floating-gate amplifier (AFGA) demonstrates that leaky FGTs may also find a use. The simplest test structures contain only a few transistors, whereas the most complex experimental chip is an implementation of a spiking neural network (SNN) which comprises thousands of active and passive devices. More precisely, it is a fully connected (256 FGT synapses) two-layer spiking neural network (SNN), where the adaptive properties of FGT are taken advantage of. A compact realization of Spike Timing Dependent Plasticity (STDP) within the SNN is one of the key contributions of this thesis. Finally, the considerations in this thesis extend beyond CMOS to emerging nanodevices. To this end, one promising emerging nanoscale circuit element - memristor - is reviewed and its applicability for analog processing is considered. Furthermore, it is discussed how the FGT technology can be used to prototype computation paradigms compatible with these emerging two-terminal nanoscale devices in a mature and widely available CMOS technology.

Regenerated cellulose ultrafiltration membranes in the treatment of pulp and paper mill process waters

Ultrafiltration (UF) is widely applied in different separation processes in the pulp and paper industry. The growing need to protect the environment, a lack of pure water and an interest in producing high-value chemicals from compounds present in process waters will probably lead to an increase in the use of UF in the pulp and paper industry. The efficiency and cost-effectiveness of a UF process depends on the applied membrane. The membrane should have a high and stable filtration capacity, a particular selectivity and a long operational lifetime. To meet these requirements a membrane should have a low fouling tendency. In addition, it should withstand the prevailing operational and chemical conditions. This thesis evaluates the performance and applicability of the regenerated cellulose (RC) membranes 00030T and C2 in the treatment of pulp and paper mill process waters based on the requirements above. The results demonstrated that both the tested RC membranes fulfilled well the requirement of high filtration capacity. In addition, in the filtration of a paper mill clear filtrate (CF) the RC membranes were not as greatly affected by variations in the CF quality as a polysulphone membrane. Furthermore, due to their extreme hydrophilicity and weak charge the fouling tendency of the membranes can be expected to be low in pulp and paper mill filtration applications. It is, however, known that fouling cannot be totally avoided even when the membrane is chosen very carefully. This study indicated that carbohydrates influenced negatively on permeability and caused fouling in the filtration of groundwood mill circulation water. Thus, a pre-treatment effectively reducing the amount of carbohydrates might help to maintain a stable capacity. However, the results of the thesis also showed that the removal of some of the possible foulants might just increase the harmful effect of others. Multivariate examination was useful in the understanding of the complicated factors causing the unstable capacity. The thesis also revealed that the 00030T and C2 membranes can be used at high pressure (max. tested pressure 12 bar). The C2 membrane, having a sponge-like substructure, was more pressure resistant, and its performance was more stable at high pressure compared to the UCO30T membrane containing macrovoids in its substructure. Both tested membranes can, according to the results, also be used at temperatures as high as 70°C in acidic, neutral and alkaline conditions. However, the use at extreme conditions might cause faster ageing of the membranes compared to ageing in neutral conditions. The thesis proved that both the tested RC membranes are very suitable for pulp and paper mill applications and that the membranes can be utilised in processes operating in challenging conditions. Thus, they could be used in more demanding applications than supposed earlier.

Spectrometrical Monitoring of Laser Sintering Process of Ceramic Material

This thesis is done as a part of project called FuncMama that is a project between Technical Research Centre of Finland (VTT), Oulu University (OY), Lappeenranta University of Technology (LUT) and Finnish industrial partners. Main goal of the project is to manufacture electric and mechanical components from mixed materials using laser sintering. Aim of this study was to create laser sintered pieces from ceramic material and monitor the sintering event by using spectrometer. Spectrometer is a device which is capable to record intensity of different wavelengths in relation with time. In this study the monitoring of laser sintering was captured with the equipment which consists of Ocean Optics spectrometer, optical fiber and optical lens (detector head). Light from the sintering process hit first to the lens system which guides the light in to the optical fibre. Optical fibre transmits the light from the sintering process to the spectrometer where wavelengths intensity level information is detected. The optical lens of the spectrometer was rigidly set and did not move along with the laser beam. Data which was collected with spectrometer from the laser sintering process was converted with Excel spreadsheet program for result’s evaluation. Laser equipment used was IPG Photonics pulse fibre laser. Laser parameters were kept mainly constant during experimental part and only sintering speed was changed. That way it was possible to find differences in the monitoring results without fear of too many parameters mixing together and affecting to the conclusions. Parts which were sintered had one layer and size of 5 x 5 mm. Material was CT2000 – tape manufactured by Heraeus which was later on post processed to powder. Monitoring of different sintering speeds was tested by using CT2000 reference powder. Moreover tests how different materials effect to the process monitoring were done by adding foreign powder Du Pont 951 which had suffered in re-grinding and which was more reactive than CT2000. By adding foreign material it simulates situation where two materials are accidently mixed together and it was studied if that can be seen with the spectrometer. It was concluded in this study that with the spectrometer it is possible to detect changes between different laser sintering speeds. When the sintering speed is lowered the intensity level of light is higher from the process. This is a result of higher temperature at the sintering spot and that can be noticed with the spectrometer. That indicates it could be possible to use spectrometer as a tool for process observation and support the idea of having system that can help setting up the process parameter window. Also important conclusion was how well the adding of foreign material could be seen with the spectrometer. When second material was added a significant intensity level raise could be noticed in that part where foreign material was mixed. That indicates it is possible to see if there are any variations in the material or if there are more materials mixed together. Spectrometric monitoring of laser sintering could be useful tool for process window observation and temperature controlling of the sintering process. For example if the process window for specific material is experimentally determined to get wanted properties and satisfying sintering speed. It is possible if the data is constantly recorded that the results can show faults in the part texture between layers. Changes between the monitoring data and the experimentally determined values can then indicate changes in the material being generated by material faults or by wrong process parameters. The results of this study show that spectrometer could be one possible tool for monitoring. But to get in that point where this all can be made possible much more researching is needed.

Feasibility study of submerged membrane bioreactor (MBR) as an alternative to conventional activated sludge process (CASP) for municipal wastewater treatment: A pilot scale study

The conventional activated sludge processes (CAS) for the treatment of municipal wastewater are going to be outdated gradually due to more stringent environmental protection laws and regulations. The Membrane bioreactors (MBRs) are the most promising modern technology widely accepted in the world of wastewater treatment due to their highly pronounced features such as high quality effluent, less foot print and working under high MLSS concentration. This research project was carried out to investigate the feasibility and effectiveness of MBR technology compare to the CAS process based on the scientific facts and results. The pilot scale MBR pilot plant was run for more than 150 days and the analysis results were evaluated. The prime focus of the project was to evaluate the correlation of permeate flux under different operating MLSS concentrations. The permeate flux was found almost constant regardless of variations in MLSS concentrations. The removal of micropollutant such as heavy metals, PCPPs, PFCs, steroidal hormones was also studied. The micropollutant removal performance of MBR process was found relatively effective than CAS process. Furthermore, the compatibility of submerged membranes within the bioreactor had truly reduced the process footprint.

Developing Supply Chain Process Management and Measurement in Global Manufacturing Company

The objective of this research is to create a current state analysis of pulp supply chain processes from production planning to deliveries to customers. A cross-functional flowchart is being used to model these processes. These models help finding key performance indicators (KPIs) which enable examinations of the supply chain efficiency. Supply chain measures in different processes reveal the changes need processes that affect the whole supply chain and its efficiency and competitiveness. Structure of pulp supply chain differs from most of the other supply chains. The fact that there are big volumes of bulk products, small product variations and supply forecasts are made for the year ahead make the difference. This factor brings different benefits but also challenges when developing supply chain. This thesis divides pulp supply chain in three different main categories: production planning, warehousing and transportation. It provides tools for estimating the functionality of supply chain as well as developing the efficiency for different functions of supply chain. By having a better understanding of supply chain processes and measurement the whole supply chain structure can be developed significantly.

Modular continuous crystallizer: operation, experimental arrangement and identification of process parameters

Crystallization is employed in different industrial processes. The method and operation can differ depending on the nature of the substances involved. The aim of this study is to examine the effect of various operating conditions on the crystal properties in a chemical engineering design window with a focus on ultrasound assisted cooling crystallization. Batch to batch variations, minimal manufacturing steps and faster production times are factors which continuous crystallization seeks to resolve. Continuous processes scale-up is considered straightforward compared to batch processes owing to increase of processing time in the specific reactor. In cooling crystallization process, ultrasound can be used to control the crystal properties. Different model compounds were used to define the suitable process parameters for the modular crystallizer using equal operating conditions in each module. A final temperature of 20oC was employed in all experiments while the operating conditions differed. The studied process parameters and configuration of the crystallizer were manipulated to achieve a continuous operation without crystal clogging along the crystallization path. The results from the continuous experiment were compared with the batch crystallization results and analysed using the Malvern Morphologi G3 instrument to determine the crystal morphology and CSD. The modular crystallizer was operated successfully with three different residence times. At optimal process conditions, a longer residence time gives smaller crystals and narrower CSD. Based on the findings, at a constant initial solution concentration, the residence time had clear influence on crystal properties. The equal supersaturation criterion in each module offered better results compared to other cooling profiles. The combination of continuous crystallization and ultrasound has large potential to overcome clogging, obtain reproducible and narrow CSD, specific crystal morphologies and uniform particle sizes, and exclusion of milling stages in comparison to batch processes.

Microsatellite variations of Quercus aquifolioides populations at varying altitudes in the Wolong Natural Reserve of China

Abstract