As the environmental concern grows, researchers try to find material which can be environmental friendly and biodegradable to some extent. At present, flax fibre cannot fully replace glass fibre. Some attempts have been made to replace the glass fibre.<p> Studies show the physical and mechanical properties of natural fibres are comparable with glass fibre, so it can replace glass fibre in the process of making biocomposites. <p> The properties of biocomposites depend on the fibre used. Research shows that to get a better biocomposite, the fibre has to be chemically treated to improve adhesion between fibre and polymer matrix. After the chemical treatment, the fibre has to be dried to minimum moisture content so the drying of flax fibre is essential in the process of making biocomposites. <p> In this research, oilseed flax fibre is dried and drying characteristics were investigated. After drying, the physical properties of the fibre were tested and analysed.<p> The fibre was dried using three different drying methods, namely, microwave, microwave-convection, and microwave-vacuum environments. Curve fitting with four empirical methods has been carried out to determine the drying constant, coefficient of determination and standard error values. The results showed that microwave-vacuum drying method is more efficient (in terms of final moisture content) than microwave and microwave-convection drying. Although microwave-vacuum drying took the most time and did not result in promising colour values, the maximum moisture removal is achieved because fibres can be dried for a longer period of time with a comparatively low temperature.<p> The results of physical properties were analysed for untreated and treated and dried flax fibre. The tensile strength and elastic modulus of untreated and treated fibre did not show any significant change. Because the diameter of flax fibre cannot be consistent, a range of values can be obtained. The diameter range of fibre bundle 30-300 µm was examined for these tests. The tensile strength obtained from these fibre bundles ranged between 16 to 667 MPa and elastic modulus values were 2 GPa up to 63 GPa.<p> The scanning electron micrograph (SEM) was also analysed for untreated and treated-dried fibre. The fibre which was dried with high power or longer period of time showed black spots, probably due to local heating. The fibre dried with microwave-vacuum developed some black spots which were clearly seen in the SEM.<p> Differential scanning calorimetric data showed a shift in temperature of degradation. In this research, degradation temperature of cellulose was found 350(+/-10)°C for the treated and dried flax fibre.<p> In conclusion, the flax fibre has a potential to be used in biocomposite production. The microwave-vacuum works best for drying where the fibre can be dried up to a less than 1% of moisture content.

The aim of this study is to investigate and compare the properties of two layer carbon epoxy composite plates manufactured using various resin impregnation techniques / Resin Transfer Molding (RTM), Light RTM (LRTM), Vacuum Assisted RTM (VARTM) and Vacuum Packaging (VP). Throughout the study a different packaging method was developed and named Modified Vacuum Packaging (BP). The mechanical properties of composite plates manufactured are examined by tensile tests, compressive tests, in-plane shear tests and their thermal properties are examined by Differential Scanning Calorimetry (DSC) and Thermo Gravimetric Analysis (TGA) tests. All tests were performed according to suitable ASTM standards. The performance of specimens from each process was observed to vary according to the investigated property / however the VP process showed the highest performance for most properties. For most of the tests, VARTM, LRTM and RTM methods were following VP process in terms of performance, having close results with each other.

<p>The thesis is based on two supplements with two major objectives. In the first supplement equilibrium top slag-steel bulk and inclusions-steel bulk were investigated by comparison between calculated and measured oxygen activity values. This was done by applying different oxide activity models for slags combined with thermodynamic calculations. In the second supplement the inclusion composition is studied during the ladle refining process. The inclusion composition is related to top slag composition and other parameters during ladle</p><p>treatment.</p><p>The work was carried out by collecting data during well controlled sampling procedures at two different steel plants. Extensive inclusion analyses in Scanning Electron Microscope, SEM, were done. The data was used together with thermodynamics for a description of the interaction between slag-steel-inclusion interaction during ladle treatment.</p><p>Evaluation of inclusion composition during the ladle refining have revealed that the majority of the inclusions belonged to the system Al₂O₃-CaO-MgO-SiO₂and showed a continuous composition change throughout the ladle refining process, from high Al₂O_3, via MgO-spinel to finally complex types rich in CaO and Al₂O_3. The final composition after vacuum treatment was found to be close to the top slag composition. Small process parameter changes and practical variations during ladle refining were proven to give large differences of the inclusion composition.</p><p>Finally, it was concluded that equilibrium does not exist between top slag and steel bulk, with respect to oxygen, for the studied conditions. However, the equilibrium does exist between the steel bulk and inclusion.</p>

Under höstterminen 2013 har Stefan Erlandsson och Louise Andersson, designingenjörsstudenter på Högskolan i Skövde, utfört ett produktutvecklingsprojekt i samarbete med entreprenören Lars Willebrand. Målsättningen för projektet var att utveckla ett lyftverktyg som ska komplettera Willebrands produktserie bestående av; travers, svängkran, plåtbyrå och lyftverktyg. Lyftverktyget ska vara anpassat för att användas i kombination med en plåtbyrå, vilket innebär att det kommer användas till att lyfta material från höga och låga höjder. Lyftverktyget måste därmed konstrueras i syfte att underlätta för användaren och undvika arbetsskador som kan uppstå vid dessa lyft. Lyftverktyget ska även kunna anpassas till kunder som endast avser att lyfta skivformade produkter i midjehöjd. Projektet inleds med en förstudie där mycket fokus läggs på ergonomi och användaren. Förstudien har gjorts genom fördjupning i relevant litteratur, kontakt med industriföretag och genom att analysera konkurrerande lyftverktyg. Resultatet från förstudien har sammanfattats till en kravspecifikation som legat till grund för konceptframtagningen. Konceptframtagningen har skett stegvis, där lyftverktygets huvudfunktioner utvecklats var för sig. De funktioner som utvecklats är justering av sugkopparnas position, manövrering och lyft vid hög/låg höjd. Alternativa lösningar har tagits fram och utvärderats för att hitta den lämpligaste lösningen på varje enskild funktion. När de bästa lösningarna hade tagits fram sattes dessa samman till ett slutgiltigt koncept. Det slutgiltiga konceptet har analyserats och detaljutvecklats. För att underlätta tillverkning och tillgodose kundens behov har många av lyftverktygets delar anpassats och ritats om. För att säkerställa att lyftverktyget lever upp till kravspecifikationen har hållfasthetsberäkningar och en antropometrisk analys genomförts. Projektets process och resultat sammanfattades och diskuterades. Slutligen gavs förslag på rekommendationer för fortsatt utveckling av lyftverktyget. / During the second semester of 2013, product design engineering students Stefan Erlandsson and Louise Andersson have been involved in a project in cooperation with entrepreneur Lars Willebrand. The main objective of this project has been to develop a lifting tool for sheet materials. The lifting tool is one of four different products developed by Lars Willebrand. The line of products also includes an overhead crane, a slewing crane and a storage drawer for metal sheets, which are already fully developed and ready for production. The purpose of this lifting tool is to be used along with the storage drawer which means that is has to be optimised for lifting sheet materials from different heights. This means that the lifting tool has to be designed with regards to the users working postures. Human factors such as ergonomics have to be taken into account as well. The initial part of the project is a pre-study with focus on ergonomics and human factors. This pre-study included a study in relevant literature, contact with a manufacturing company and an analysis of the possible competitor’s lifting tools. The results from the pre-study have further been used to define the specification of requirements, which is the foundation for the concept development. The concept development has undergone a number of different phases. All of the lifting tool’s main functions were broken down and developed individually. The functions were as follows; adjustment of the suction cups, lifting from different heights and handling. The most suitable solution for each main function were chosen and assembled into one final concept. The final concept has been analysed and further developed in order to please the employer and the users of the lifting tool. Some details in the design have been changed in order to ease the manufacturing of the lifting tool. To ensure that the final concept matches the specification of requirements, strength calculations and FEM analysis have been made and anthropometrical measurements have been taken into account. The final chapters include a discussion and recommendations for further development of the lifting tool.

Graphene, a two-dimensional counterpart of three-dimensional graphite, has attracted significant interest, due to its distinctive electrical and mechanical properties, for developing electronic, optoelectronic, and sensor technologies. In general, doping of graphene is important, as it gives rise to p-type and n-type materials, and it adjusts the work function of the graphene. This adjustment is necessary in order to control charge injection and collection in devices such as solar cells and light emitting devices. Current methods for graphene doping involve high temperature process or interactions with chemicals that are not stable. Moreover, the process of transferring graphene from its growth substrate and its exposure to the environment results in a host of chemical groups that can become attached to the film and alter its electronic properties by accepting or donating electrons/holes. Intentional and controllable doping of the graphene, however, requires a deeper understanding of the impact of these groups. The proposed research will attempt to clarify the unintentional doping mechanism in graphene through adsorption or desorption of gas/vapor molecules found in standard environments. A low temperature, controllable and defect-free method for doping graphene layers will also be studied through modifying the interface of graphene and its support substrate with self-assembled monolayers (SAMs) which changes the work function and charge carriers in the graphene layer. Furthermore, current methods of chemical vapor deposition synthesis of graphene requires the film to be transferred onto a second substrate when the metal layer used for growth is not compatible with device fabrication or operation. To address this issue, the proposed work will investigate a new method for wafer scale, transfer-free synthesis of graphene on dielectric substrates using new carbon sources. This technique allows patterned synthesis on the target substrate and is compatible with standard device fabrication technologies; hence, it opens a new pathway for low cost, large area synthesis of graphene films.

No description available.

No description available.

Dominated by Heisenberg's uncertainty principle, vacuum is not quantum mechanically an empty void, i.e. virtual pairs of particles appear and disappear persistently. This nonlinearity subsequently provokes a number of phenomena which can only be practically observed by going to a high-intensity regime. Pair production beyond the so-called Sauter-Schwinger limit, which is roughly the field intensity threshold for pairs to show up copiously, is such a nonlinear vacuum phenomenon. From the viewpoint of Dirac's front form of Hamiltonian dynamics, however, vacuum turns out to be trivial. This triviality would suggest that Schwinger pair production is not possible. Of course, this is only up to zero modes. While the instant form of relativistic dynamics has already been at least theoretically well-played out, the way is still open for investigating the front form. The aim of this thesis is to explore the properties of such a contradictory aspect of quantum vacuum in two different forms of relativistic dynamics and hence to investigate the possibility of finding a way to resolve this ambiguity. This exercise is largely based on the application of field quantization to light-front dynamics. In this regard, some concepts within strong field theory and light-front quantization which are fundamental to our survey have been introduced, the order of magnitude of a few important quantum electrodynamical quantities have been fixed and the basic information on a small number of nonlinear vacuum phenomena has been identified. Light-front quantization of simple bosonic and fermionic systems, in particular, the light-front quantization of a fermion in a background electromagnetic field in (1+1) dimensions is given. The light-front vacuum appears to be trivial also in this particular case. Amongst all suggested methods to resolve the aforementioned ambiguity, the discrete light-cone quantization (DLCQ) method is applied to the Dirac equation in (1+1) dimensions. Furthermore, the Tomaras-Tsamis-Woodard (TTW) solution, which expresses a method to resolve the zero-mode issue, is also revisited. Finally, the path integral formulation of quantum mechanics is discussed and, as an alternative to TTW solution, it is proposed that the worldline approach in the light-front framework may shed light on different aspects of the TTW solution and give a clearer picture of the light-front vacuum and the pair production phenomenon on the light-front.

Magistro darbe analizuotos vakuuminių saulės kolektorių, skirtų vandeniui šildyti sistemos energetiniai parametrai, rodikliai ir konstrukcijos. Taip pat šiame darbe nagrinėjama vakuuminio saulės kolektoriaus energetinės charakteristikos. Darbą sudaro dvi dedamosios dalys: analitinė ir praktinė darbo dalys. Analitinėje dalyje apžvelgtos skirtingų tipų saulės kolektorių charakteristikos, saulės kolektorinių vandens šildymo sistemų veikimo principas ir panaudojimo galimybės. Trumpai apžvelgta perteklinės energijos panaudojimo galimybės ir saulės kolektorių sistemos projektavimo principas. Praktinėje darbo dalyje tirta saulės kolektorinė vandens šildymo sistema gamybinėmis sąlygomis. Atskleistas sistemos veikimo mechanizmas, ištirtas kolektorių našumas skirtingomis darbinėmis sąlygomis. Darbo pabaigoje suformuluotos atlikto tyrimo išvados. Pateiktos rekomendacijos tirtos saulės kolektorinės vandens šildymo sistemos administraciniam personalui. / Master's thesis analyses vacuum solar collectors for water heating system energy parameters, indicators and construction. Also vacuum solar collector system energy characteristics. The work consists of two component parts: the analytical and practical parts of the research. In the analytical part is an overview of the different types of solar collector performance, solar water heating systems operation and utilization. Short overview of surplus energy utilization possibilities and solar system design principle. In the practical part of the thesis is investigated solar collector water heating system under production conditions. Revealed mechanism of the system, investigated thermal performance under different operating conditions. In the end of research thesis conclusions are formulated. Recommendations were given for tested solar collector water heating system administrative personnel.

Das saisonale Auftreten von erdig/modrigen Geruchsstoffen beeinträchtigt die organoleptische Qualität von Trinkwasser aus Talsperren weltweit. Grund für diese Beeinträchtigungen sind biogene Geruchsstoffe, die in oligo- bis mesotrophen Trinkwassertalsperren vorwiegend von benthischen Cyanobakterien freigesetzt werden. Als wichtigste Vertreter der biogenen Geruchsstoffe in den untersuchten sächsischen Trinkwassertalsperren wurden Geosmin und 2-Methylisoborneol (2-MIB) identifiziert, die bereits in Konzentrationen von wenigen ng/L organoleptisch wahrgenommen werden. Zur Entfernung der Geruchsstoffe während der Trinkwasseraufbereitung wird meist die Adsorption an Pulveraktivkohle als zusätzlicher Aufbereitungsschritt eingesetzt. In natürlichen Wässern wird die Adsorptionskapazität vor allem durch die direkte Konkurrenz niedermolekularer, gut adsorbierbarer Fraktionen des organischen Hintergrundes reduziert. Es konnte gezeigt werden, dass die Adsorption mit verschiedenen Modellansätzen für die Gemischadsorption von Spurenstoffen und organischem Hintergrund beschrieben werden kann. Diese Modelle, die für Gleichgewichtszustände entwickelt wurden, können auch angewendet werden, wenn sich das Adsorptionsgleichgewicht noch nicht eingestellt hat, wie es oftmals bei den in der Praxis realisierten Kontaktzeiten der Fall ist. Bei Auswahl einer Aktivkohle mit guter Entfernungsleistung für die Geruchsstoffe liegen die Kosten für die benötigte Aktivkohlemenge zur Reduzierung der Geruchsstoffkonzentration um 90 % bei 0,009 - 0,05 €/m³. Der Einsatz UV-basierter erweiterter Oxidationsverfahren, wie UV/O3, UV/H2O2, Vakuum-UV (VUV) sowie VUV/O3, stellt eine Alternative für die Entfernung von Geosmin und 2-MIB dar. Die eingehende Untersuchung dieser Verfahren zeigte, dass die indirekte Oxidation durch gebildete Hydroxylradikale zu einer effektiven Umsetzung der Geruchsstoffe und zahlreicher weiterer Spurenstoffe führt. Zusätzlich wird das Rohwasser aufgrund der keimtötenden Wirkung von UV-Strahlung (und Ozon) gleichzeitig desinfiziert. Allerdings sind bei den Verfahren UV/O3 und UV/H2O2 für einen kosteneffizienten Geruchsstoffabbau hohe Oxidationsmittelkonzentrationen notwendig, die zu unerwünschten Nebenprodukten oder Residuen führen können. Die VUV-Bestrahlung stand besonders im Fokus der Untersuchungen, da dieser Wellenlängenbereich sowohl zur photoinitiierten Oxidation von Spurenstoffen als auch zur Generierung von Ozon in der Gasphase eingesetzt werden kann. Ozongenerierung und Bestrahlung (im UV- oder VUV-Bereich) wurden in einem speziellen UV-Reaktor mit nur einer Strahlungsquelle realisiert. Mit diesem innovativen UV-System mit interner Ozongenerierung konnte eine Reduzierung der Geosminkonzentration um 90 % mit einem Energieverbrauch unter 1 kWh/m³ und Energiekosten unter 0,09 €/m³ erreicht werden. Außerdem wird Nitrit, das durch VUV-Bestrahlung gebildet wird, durch die Zugabe des intern erzeugten Ozons oxidiert. Unter den untersuchten UV-basierten Verfahren ist die Kombination VUV/O3 mit interner Ozongenerierung für die Entfernung von saisonal auftretenden Geruchsstoffen in der Trinkwasseraufbereitung aus Talsperrenwässern am besten geeignet. Die Verfahrenskombination zeichnet sich durch ein geringes Risiko hinsichtlich der Bildung unerwünschter Nebenprodukte, den Verzicht auf den Einsatz von Chemikalien und die Vermeidung von Rückständen sowie einen vergleichsweise geringen Energieverbrauch und Wartungsaufwand aus. / The seasonal occurrence of earthy/musty odours affects the organoleptic quality of drinking water from reservoirs worldwide. In oligo-mesotrophic drinking water reservoirs this impairment is mainly caused by biogenic odour compounds released by benthic cyanobacteria. The most important odour compounds in the investigated Saxon drinking water reservoirs were geosmin und 2-methylisoborneol (2-MIB), which exhibit a threshold odour concentration of several ng/L. The application of powdered activated carbon is widely used for the removal of odour compounds during drinking water treatment. However, the adsorption capacity in natural waters is reduced due to the competition of well adsorbable, low molecular weight organic compounds. It could be shown that the adsorption process can be described with various model approaches for the competitive adsorption of micropollutants in presence of natural organic matter. These model approaches, which were developed for equilibrium adsorption, can be applied for the non-equilibrium adsorption as well, for example for contact times realized in the waterworks. If an activated carbon with a high adsorption capacity for odour compounds is applied, the costs for the amount of activated carbon necessary to reduce the odour concentration by one order of magnitude are about 0.009 - 0.05 €/m³. UV-based advanced oxidation processes like UV/O3, UV/H2O2, Vacuum-UV (VUV) and VUV/O3 are an alternative for the removal of geosmin and 2-MIB. Thus, these processes were investigated in detail showing that an effective elimination of the odour compounds and other micropollutants is achieved via indirect oxidation by formed hydroxyl radicals. Additionally, the raw water is disinfected by the germicidal effect of UV irradiation (and ozone). However, for a cost efficient degradation of odour compounds by UV/O3 or UV/H2O2 high oxidant concentrations are necessary, which lead to the formation of undesired by-products and residuals. The focus of the presented doctoral thesis was on the treatment with VUV irradiation because this wavelength range can be applied for photoinitiated oxidation as well as for the generation of ozone in the gas phase. Ozone generation and irradiation (in the UV or VUV range) can be combined in a specific UV reactor using a single irradiation source. Using this innovative UV system with internal ozone generation the reduction of the concentration of geosmin by one order of magnitude can be achieved with an energy consumption below 1 kWh/m³ and operational costs below 0.09 €/m³. Furthermore, the addition of ozone leads to a noticeable oxidation of nitrite, which is formed under VUV irradiation. Within the investigated UV based processes, the combination VUV/O3 with internal ozone generation is the most suitable for the removal of seasonally occurring odour compounds during drinking water treatment from reservoir water. The process is characterized by the minimization of the risk for the formation of undesired by-products without the application of chemicals, the reduction of the formation of residues as well as low energy consumption and maintenance requirements.