Die Durchströmungswäsche von Filterkuchen aus innenporösen Partikeln wird anhand von makro- und mesoporösen Kieselgelen untersucht. Die Filterkuchenbildung der KCl-haltigen Suspensionen erfolgt in einer Drucknutsche nach VDI-2762-2. Die Filterkuchen werden über einen perforierten Stempel mit entionisiertem Wasser durchströmt und der Wascherfolg über die Bilanzierung der K+-Ionen ermittelt. Die Porosität der Kieselgel-Filterkuchen beträgt 80 %, wobei sich 50 % der gesamten Mutterlauge in den Innenporen befindet. Dennoch zeigen sich mit 1 % Restbeladung ähnliche Waschergebnisse wie für unporöse Feststoffe (Quarz und Glas). Die Innenporen werden gereinigt, der in der Literatur postulierte ausgeprägte Diffusionsbereich in der Waschkurve wird nicht sichtbar. Berechnungen nach CARMAN-KOZENY, FICK und mittels dimensionsloser Kennzahlen verdeutlichen, dass Perfusion und Diffusion die Wäsche poröser Systeme beeinflussen. Die vorgestellten Modelle eignen sich auch für die Anwendung in der Praxis. / The displacement washing of filter cakes consisting of porous particles is investigated using macro- and mesoporous silica gels. The filter cakes of KCl-containing suspensions are formed in a pressure filter device according to VDI-2762-2. The filter cakes are flown through with deionized water via a perforated piston and the washing success is determined by balancing the K+ ions. The porosity of the silica gel filter cakes is 80 % and 50 % of the mother liquor is trapped in the inner pores. Nevertheless, with 1 % residual loading, washing results are similar to those for non-porous solids (quartz, glass). The inner pores are cleaned, the distinct diffusion region in the washing curve postulated in the literature is not visible. Calculations according to CARMAN-KOZENY, FICK and by means of dimensionless quantities illustrate that both perfusion and diffusion influence the washing of porous systems. The presented models are also suitable for practical applications.

The study aims to examine (1) the extent to which EFL learners in upper secondary school use feedback comments from teachers and peers to revise their texts and how the usage patterns vary by type of feedback approach, (2) how the students use feedback to revise their texts and how the usage patterns vary by type of feedback approach, and (3) What positive or negative effects the type of feedback approach has on students’ revisions. Moreover, the study aims to investigate the extent the type of feedback approach affects students’ usage patterns in their revisions. The findings will provide a basis for discussions about the possible qualities of written feedback that could be included to help students improve their writing skills. Content analysis of 28 argumentative essays written by first-year upper secondary students in Sweden is used to identify the type of feedback provided by teachers and peers and the type of revisions made by the students. Using the identified types of feedback and revisions, a text analysis was adopted to examine the frequency of feedback and revisions, and how students used it to revise their text. Furthermore, the results are presented and compared to different relevant studies (e.g., Baker, 2016; Lee; 2008) and theories such as Krashen's (1985) input hypothesis and Swain's (2005) output hypothesis, to draw some insights into the effects of feedback on students' revisions. The results show that students utilized corrective feedback on the micro level more than the macro level – especially indirect corrective feedback on the micro level. The students used most of the feedback to revise their errors on the micro level such as grammar, spelling, and punctuation; however, a few revisions were made on the macro level where students improved their text by restructuring their arguments and ideas. Finally, the findings indicate that formative feedback had a positive effect on students' revisions both on the macro and micro level where students improved the coherence and cohesion of their texts in the final draft. Therefore, if formative feedback is applied in the appropriate context, it may help students develop their writing abilities.

The financial stability of banks is crucial if they are to fulfil their role in facilitating transactions between borrowers and lenders. The purpose of this study was to investigate the effect of credit risk on the South African banking industry following a movement in credit ratings by rating agencies. Data from a sample of 11 banks were collected from 2006 to 2015. Econometric regression analysis was used to analyse the data. The results show that inflation, credit ratings, exchange rate, gross domestic product, unemployment rate, capital adequacy ratio and size of the bank are significant factors that determine "non-performing loans". Therefore, it is imperative that banks continuously monitor these factors and adapt their credit policies on "non-performing loans". This action would prepare banks for any adverse effects and ensure that the banking industry remains a sound and efficient contributor to the growth of the South African economy. / Business Management / M. Com. (Business Management)

La préservation de l’environnement et des ressources naturelles pour les prochaines générations est aujourd’hui considérée comme un des axes les plus prioritaires dans presque tous les secteurs économiques. Le secteur des Technologies de l’Information et de la Communication est loin d’être épargné de cette tendance écologique. Nous considérons dans cette thèse la problématique de la conservation d’énergie dans le contexte technologique actuel caractérisé par: • La coexistence d’une multitude de technologies d’accès sans fil offrant un environnement riche et dynamique • Des terminaux mobiles multimodaux • Limitations persistantes des sources d’énergie sur les terminaux mobiles. Dans ce contexte très riche, les possibilités offertes aux usagers sont à double tranchant. D’un côté, elles peuvent très bien améliorer la QoS en offrant toujours la meilleure connectivité en fonction du contexte de l’utilisateur. D’un autre côté, et sans une bonne optimisation de la consommation d’énergie sur le terminal, la disponibilité de celui-ci peut vite diminuer et donc faire baisser la QoE à cause de l’énergie nécessaire pour gérer plusieurs interfaces radio en parallèle. Nous considérons essentiellement les liens entre les stations de base (ou les point d’accès) et les terminaux mobiles. Notre objectif étant d’analyser la consommation d’énergie sur ces liens pour ensuite proposer des contributions permettant de mieux la maitriser. Nous focalisons essentiellement sur l’exploitation des multiples interfaces et du multi-flux pour étudier, analyser et proposer des solutions dynamiques et adaptatives d’ordonnancement, de sélection et de gestion d’interfaces minimisant la consommation d’énergie / Since the last decades, environmental issues are becoming among the major concerns for most human activities, including the Information and Communication Technologies sector. This will surely influence upcoming networking technologies, architectures and usage practices. New approaches and methodologies are required in order to evaluate and to reduce the Carbon Footprint toward what is commonly denoted as Green Networks. Within the ICT sector, the main efforts are related to energy saving techniques. These efforts started in early stages within wireless technologies, mainly because of energy limitations on mobile devices such as mobile phones and wireless sensors. Additionally, because of health considerations, standardization bodies and government had set stringent policies and limits on electromagnetic radiation levels that can be emitted by radio stations. For these reasons, many academic and industrial research and development activities had led to a number of relatively energy efficient solutions. In this thesis, we consider energy efficiency in the context of Heterogeneous Wireless Access Networks. These are composed of multi-standards wireless network solutions, with non uniform topologies and cell sizes and Multi-Modal mobile terminals able to manage simultaneously different connections. The main contributions of our studies include the proposal of new optimization solutions regarding user association and scheduling techniques at both flow and packet levels for multi-homed mobile terminals. An overall context-based solution is also proposed in order to provide end-to-end energy efficient networking solutions

The aim of the work is to describe procedural texturing and usage of a noise for creating textures of real materials. The reader will learn the fundamentals of the noise, its properties and a way of using it. Random numbers and interpolation methods are important parts of the noise evaluations, therefore there are chapters about random numbers generating and interpolation methods. Obviously, there is not missing the chapter, which is depicting properties and principles of several methods of creating noise. The main part of this work is effective implementation of library with a chosen noise methods, so next chapters are about choosing methods and design of the interface, implementation and many kinds of tests and optimalizations. Achieved results and final conclusions are at the end of this work.

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In der vorliegenden Arbeit wird die Entwicklung eines kinetischen Energy Harvesters vorgestellt, der auf Grundlage des elektrostatischen Wandlerprinzips aus Vibrationen elektrische Energie generiert. Für die Umsetzung wurde eine Siliziummikrostruktur entworfen, die für Arbeitsfrequenzen unter 100 Hz ausgelegt ist. Die Zahnstruktur der verwendeten Elektroden ermöglicht Spaltabstände im Submikrometerbereich und folglich große Kapazitätsänderungen, die durch die Elektrodengeometrie zusätzlich mit einer höheren Frequenz als die mechanische Bewegung stattfinden. Vergleichsweise große Leistungsausbeuten und geringe Quellimpedanzen sind dadurch erreichbar. Die geometrischen Parameter der Elektroden wurden unter Berücksichtigung der auftretenden Fertigungstoleranzen und Wechselwirkungen zueinander optimiert. Für die Ausnutzung einer ausreichend großen Inertialmasse wurde ein feinwerktechnisch hergestellter Hebelmechanismus an die Mikrostruktur angekoppelt. Über diesen wird zusätzlich ein neuer Ansatz zur Abstimmung der Eigenfrequenz des Harvesters umgesetzt. Experimentelle Untersuchungen zeigten Ausgangsleistungen im einstelligen Mikrowattbereich bei Anregungen im Zehntel m/s²-Bereich. Durch fortschreitende Optimierungen der Fertigungstechnologie sind noch deutliche Leistungssteigerungen um mindestens zwei Größenordnungen möglich. Weiterhin wird ein Energiemanagementsystem vorgestellt, welches die effiziente Übertragung der Energie auf den Verbraucher ermöglicht. / In this work the development of a kinetic energy harvester using the electrostatic conversion principle is presented. The silicon microstructure is designed to work in frequency ranges below 100Hz. Its toothed electrode structure enables gap distances in the sub micrometer range and consequently high changes of capacitance. Additionally, due to the electrode geometry the frequency of the capacitance changes is higher then the frequency of the mechanical movement. Thus high power outputs and low source impedances can be reached. The electrodes geometric parameters were optimized considering manufacturing tolerances and interactions of the parameters. To reach a sufficient inertial mass, a lever mechanism manufactured by precision engineering was connected to the microstructure. This mechanism also allows the implementation of a new method of frequency tuning. In experimental tests power outputs in the single digit microwatt range under excitations of 0.3 m/s² were reached. In accordance of further optimizations of the manufacturing technology significantly higher outputs, by at least two orders of magnitude, are possible,. Furthermore an energy management system is presented, that allows the efficient transfer of the electrical energy to the consumer.

Cutting movement is still one of the main means to obtain the desired machined surface. As the most representative cutting method in subtractive manufacturing, milling is widely used in industrial production. However, the chatter induced by the dynamic interaction between machine tool and process not only reduces the accuracy of the machined workpiece, but also increases the tool wear and affects the rotary accuracy of the spindle. The stability lobe diagram can provide stable machining parameters for the technicians, and it is currently an effective way to avoid chatter. In fact, the dynamic interaction between the machine tool and process is very complicated, which involves the machine tool, milling tool, workpiece and fixture. The induced mechanism of chatter depends on different machining scenarios and is not entirely dependent on the vibration modes of milling tool. Therefore, it is important to obtain stable machining parameters and to know the dynamic surface location error distribution, which can ensure machining quality and improve machining efficiency. In this dissertation, two methods for constructing stability lobe diagram are first introduced, and then two machining scales, macro milling and micro milling, are studied. For the macro-milling scale, the dynamic response of the in-process workpiece with time-varying modal parameters during the material removal process is analyzed. The stability lobe diagrams for thin-walled workpiece and general workpiece with continuous radial immersion milling are established respectively. Besides, the cumulative surface location error distribution is also studied and verified for the general workpiece. For the micro-milling scale, the dynamics at the micro-milling tool point is obtained by means of the receptance coupling substructure analysis method. The stability lobe diagram and surface location error distribution are analyzed under different restricted/free tool overhang lengths. The relationship between measurement results and burrs is further explained by cutting experiments, and the difference between the two milling scales is compared in the end.

Non-exhaust PM10 is an issue in the urban environment linked to health issues. Emissions of non-exhaust PM10 is relatable to pavement properties. Also of importance is resuspension of road dust stored from surfaces. This depends on the traffic and metrological conditions. Given this, the purpose of the thesis was to give an overview limited to Sweden and the Nordic countries regarding non-exhaust PM10 emissions and road dust. The overview includes how particles are related to human health. Also included is the principle of how particles are emitted from road surface and tyre interaction, both directly and through resuspension of road dust. This thesis also includes an overview of how the use of studded tyres impact on asphalt surfacings and how the properties of the materials used impact on the abrasion wear. This is then linked to the emissions of non-exhaust particles. Further described is how measurements can be done of ambient particles and road dust, followed on two major models for road abrasion wear and non-exhaust PM prediction. Also included is how road operation, e.g. traction sanding and dust binding, influence the particle emissions together with other options to reduce the emissions through, e.g. limiting the use of studded tyres. One special issue discussed in this thesis is the lack of holistic view regarding the environmental problems in the urban environment with focus on particle emissions and road noise emissions, both from the road surface and tyre interaction. Currently the most problematic issue is prioritized and the resulting solution to that specific problem might increase other problems. This thesis shows that much knowledge is available regarding non-exhaust PM10 emissions and road dust, but also that several knowledge gaps exists. Several suggestions on further studies is given together with a brief overview on the continued work forward from this thesis. / Icke-avgasemissioner av PM10 är ett problem i urbana miljöer länkat till flera hälsoaspekter. Dessa emissioner kan relateras till beläggningars egenskaper. Även resuspension av vägdamm från ytor är av betydelse och beror på både trafiken och meterologin. Baserat på detta är syftet med denna avhandling att ge en översikt kring icke-avgas PM10 emissioner och vägdamm, begränsat till Sverige och de övriga nordiska länderna. Denna översikt inkluderar hur partiklar relaterar till människans hälsa. Annat som inkluderas är hur partiklarna emitteras från vägyta-däckinteraktionen, både direkt och genom resuspension av vägdamm. Avhandlingen inkluderar även en översikt kring hur användandet av dubbdäck inverkar på vägbeläggningar och hur dess egenskaper inverkar på nötningsslitage. Detta länkas därefter till partikelemissioner. Vidare beskrivs även hur mätningar kan genomföras av partiklar samt vägdamm vilket följs upp av beskrivningar kring två större modeller kring prediktion av nötningsslitage och prediktion av icke-avgasemissioner. Även hur driftåtgärder inverkar på emissionerna tillsammans med alternativ för att minska emissionerna tas upp. Ett särskilt problem som tas upp i avhandlingen är bristen på helhetssyn beträffande miljöproblem i den urbana miljön med fokus på partikel- och bulleremissioner från vägyta-däckinteraktionen. För närvarande brukar det värsta problemet prioriteras och lösningen till det detta problem kan i sin tur medföra att andra miljöproblem istället förvärras. Denna avhandling visar på att mycket kunskap existerar kring icke-avgasemissioner av PM10 och kring vägdamm, men även att flertalet kunskapsluckor existerar. Flertalet förslag på vidare studier ges tillsammans med en överblick kring det fortsatta arbetet. / <p>QC 20180202</p>

The rise of superbugs, including antibiotic-resistant bacteria, and virus outbreaks, such as the recent coronavirus scare, illustrate the need for rapid detection of disease pathogens. Widespread availability of rapid disease identification would facilitate outbreak prevention and specific treatment. The ARROW biosensor microchip can directly detect single molecules through fluorescence-based optofluidic interrogation. The nature of the microfluidic channels found on optofluidic sensor platforms sets some of the ultimate sensitivity and accuracy limits and can result in false negative test results. Yet higher sensitivity and specificity is desired through hydrodynamic focusing. Novel 3D hydrodynamic focusing designs were developed and implemented on the ARROW platform, an optofluidic lab-on-a-chip single-molecule detector device. Microchannels with cross-section dimensions smaller than 10 μm were formed using sacrificial etching of photoresist layers covered with plasma-enhanced chemical-vapor-deposited silicon dioxide on a silicon wafer. Buffer fluid carried to the focusing junction enveloped an intersecting sample fluid, resulting in 3D focusing of the sample stream. The designs which operate across a wide range of fluid velocities through pressure-driven flow were integrated with optical waveguides in order to interrogate fluorescing particles and confirm 3D focusing, characterize diffusion, and quantify optofluidic detection enhancement of single viruses on chip.