Amorphous silicon carbide solar cells fabricated using ECR-PECVD

Solar power is becoming important as an alternative energy source. Solar power generation utilizes solar cells, which generates DC electricity when light falls on them. Attractive materials for solar energy conversion are amorphous silicon (a-Si) and its alloys, such as amorphous silicon carbide (a-(SiC)). Although research on a-Si solar cells has been carried out in many countries since the 1970\u27s, a-(SiC) solar cells have not been widely studied. Amorphous silicon carbide has a wider bandgap than amorphous silicon; therefore, we can expect to have solar cells with larger open-circuit voltage and high conversion efficiency for the high-energy spectrum in tandem-cell arrangement. High bandgap combined with good material quality leads to an increase in open-circuit voltage. The work presented here explores the relationship between photovoltaic properties and growth conditions of amorphous silicon carbide solar cells. With this, we are able to determine a good fabrication technique for making a-SiC:H solar cells. In this thesis, we study film quality by measuring Urbach energy, E₀₄ and Tauc gaps, photo and dark conductivities, mobility-lifetime product, and activation energy.This report also studies the variation of these properties as functions of the growth conditions, such as substrate temperature, microwave power, chamber pressure, gas ratios, and doping levels. Then we applied the best growth conditions for making intrinsic and doped amorphous silicon carbide materials to produce good p-i-n solar cells. We found that a deposition pressure of 10 mTorr, a substrate temperatures of 300 to 350ðC, and CH₄/(CH₄+SiH₄) flows of 0.6 to 0.7 can produce very good amorphous silicon carbide solar cells. These solar cells have an open-circuit voltage of 0.96 V, and a fill factor of 0.71. We also found that our materials have superior quality compared to materials reported previously in the literature

Rapid Detection and Quantification of Mycobacterium Tuberculosis Using Single-Based Extension and Capillary Electrophoresis

In 1993, the World Health Organization (WHO) has declared tuberculosis (TB) a global emergency. Since then, more than 30 million lives have been claimed by that world-wide epidemic. In 2011, 8.7 million people “felt ill†because of TB and not all TB cases were reported to clinicians. Therefore, it is important to accurately identify TB patients by developing a diagnostic method that is sensitive, fast, and cost-effective. However, conventional methods have not met those criteria because they either require lengthy procedures or may misdiagnose TB cases. Hence, the automated Xpert MTB/RIF, endorsed by WHO in 2010, was developed and so far has been capable of quickly detecting TB and rifampicin resistant TB strains and producing test results in less than 100 minute. However, the Xpert MTB/RIF may leave out other drug-resistant TB strains which are equally important and in need of diagnoses. Therefore, we would like to utilize single-based extension and capillary electrophoresis (SBE-CE), a method that promises to identify all strains of Mycobacterium tuberculosis and possibly any mycobacterium. The main purpose of this study is to generate a calibration curve of the electrophoretic peak areas produced by CE versus the corresponding sample concentrations of DNA solutions. For initial proof of concept, algal DNA’s were also used to produce the calibration curves. The curves established a linear trend but with distinct slopes, possibly due to different fluorescent dyes used in SBE reactions

Formative Assessment in Teaching and Learning EFL

Formative assessment in EFL in Vietnam has previously been marginalized; however, there is now recognition of its important role for generating fair and reliable characterizations of students’ performances which cannot be solely made by summative assessments. The presenter will therefore draw attendees’ attention to distinctive features of formative assessment

ATLAS detector with cosmic rays and expected performance with early data

Cosmic muons have helped to understand the ATLAS detector in terms of DAQ, trigger, alignment and calibration. I briefly review the performance of the ATLAS Inner Detector, Calorimeters and Muon Spectrometer systems with cosmic rays. The expected performance with first LHC collisions will also be reviewed

Accurate overbraiding simulations for complex mandrels:On the role of yarn interactions

Overbraiding is a process to manufacture tubular structural components at a high deposition rate. Composite product development using overbraiding and subsequent infusion can be both costly and time-intensive. This procedure often requires multiple iterations to meet design specifications. To reduce the associated expenses and time investments, simulation tools for overbraiding processes prove to be valuable. Various approaches exist, ranging from straightforward analytical models to computationally intensive finite element methods. Earlier developed kinematic models provide fast computations for complex geometries, making them suitable for design purposes. These models neglect yarn interactions, which reduces the computational cost, but also compromises the accuracy of the model predictions.The aim of this thesis is to develop an efficient yarn interaction model to enhance the accuracy of overbraiding simulations for practical design of components with complex mandrel shapes, improving the accuracy but without severely impairing the computational performance of the kinematic model. To this end, the following three problems are addressed:First, a yarn interaction model was developed for biaxial and triaxial braid patterns. The model considers the stick-slip process at the cross-over point between yarns and at the yarn-ring contact. Subsequently, the solution was implemented in a multiple contact points model employing a fast iterative frontal approach to solve force equilibrium for the braid as a whole. Validations of the overbraiding models against experimental data, encompassing axisymmetric and non-axisymmetric cases, demonstrate a substantial improvement in predictions compared to earlier published simulation results.Second, an experimental setup was developed to measure the yarn-to-yarn coefficient of friction as a function of the inter-yarn angle and normal contact force. Friction between carbon and glass contact pairs was investigated under both dry and water-lubricated conditions. A mesoscopic friction model was introduced to capture the measured impact of the inter-yarn angle and normal force on the dynamic friction coefficient. Notably, observations indicate the formation of a water bridge at the contact interface during wet testing. Furthermore, it is argued that the additional contribution of capillary forces results in consistently higher friction coefficients for yarns lubricated with water compared to dry yarns.Finally, overbraiding simulations for both biaxial and triaxial processes were conducted to investigate the impact of process configurations and friction data on the simulation outcomes. The findings revealed effects of the yarn interactions on braid angles during both the steady and unsteady states of the process. This improved accuracy of the models is achieved with increased computational cost, yet remaining within acceptable range for design and optimization purposes

Membrane Surface Engineering for Biochemical Applications

Synthetic membranes have been frequently used for many fields, such as, the food and beverage, biopharmaceutical, and biofuel industries. In the beer industry, microfiltration frequently suffers from fouling due to the interaction between different species. It is shown that polyphenols can form cross-links with protein molecules, forming insoluble aggregates. However, by adding an optimal amount of polysaccharides these aggregates can be disrupted thus reducing fouling by the aggregates. Confocal laser scanning microscopy (CLSM) is a powerful technique to locate the foulants inside the wet membrane in order to understand more about the behavior of fouling in microfiltration. Membrane surface modification is used to impart desirable membrane surface properties. Here membrane surface modification is used to develop membrane adsorbers for protein purification. Hydrophobic interaction membrane chromatography (HIMC) has gained interest due to its excellent performance in purification humanized monoclonal antibodies. HIMC affords all the advantages of membrane adsorbers, which is dynamic capacities that are independent of flow rate, higher throughput and easy to scale up. Unique inverse colloidal crystal (ICC) membranes were developed with highly periodic structures, high porosity, and fully interconnected pores. ICC membranes offer a very high binding capacity for IgG4. On the other hand, salt responsive membranes were developed by grafting responsive ligand, poly vinylcaprolactam (PVCL), from the surface of the membrane by atom transfer radical polymerization (ATRP). The nanostructure can vary its conformation and hydrophobicity when the temperature changes. After modification, membrane is able to provide a very high recovery and yield. Membrane modification is also well applied for biofuel industry. Duel nanostructures, poly styrene sulfonic acid (PSSA) and poly ionic liquid (PIL) were grafted separately and neighborly from the surface of ceramic membrane substrate by control ATRP and UV initiated radical polymerization. Modified membrane substrates were challenged with cellulose and corn-stovers biomass hydrolysis in pure ionic liquid (IL) and mixture of IL and co-solvent. High yield in total reducing sugar (TRS), 95% and 60% for cellulose and corn-stovers biomass respectively, indicates strong activity of polymeric solid acid catalysts