This study investigated the incorporation of student video production into Year 7 science classes and determined associated learning benefits. Availability of digital cameras and movie editing software make student in-class video production a possibility. However, the introduction of technology into classrooms often precedes an understanding of its effective utilisation. While the science classroom was ideal to utilise the audio/visual benefits of video production, a framework to streamline and guide students’ production was needed to ensure productive learning. The writing-to-learn in science model (Prain & Hand, 1996a) and Science Writing Heuristic (Hand & Keys, 1999) were selected to fulfil this role. The adaptation of the writing-to-learn in science model to include video production as a text type coincided with a call from Prain (2006) to extend research to determine the influence of “new technology-mediated, multimodal learning environments” (p. 79) on students’ science learning. Two intact Year 7 classes conducted the same science investigation following the writing-to-learn in science model, one class (Yr 7A, N = 21) used digital video to record and report their findings while the other class (Yr 7B, N = 22) used a traditional method of poster making. Students worked in mixed gender and ability groups of three. Data instruments included pretest, posttest, delayed posttest, a repeated question instruments, and content analysis of the students’ final products. Two groups from each class were video tracked throughout their investigations and were later interviewed. Video data were transcribed and analysed to determine patterns of learning behaviour. This study showed that video production fits comfortably into the writing-to-learn in science framework. Making videos in science delivered learning advantages through the audio/visual nature of video production and the learning behaviours the production process elicited. The nature of video, as a visual and oral medium, allowed students to capture their science investigations accurately and then continue to manipulate the content through reviewing and editing. Through video production, students demonstrated heightened awareness of, and responsibility for, the learning of their audience that led to rehearsal of science concepts before filming. Data analysis revealed that video students collaborated, used higher order thinking, and engaged in the underlying scientific concepts more than the poster makers. This study is significant as it explores in a science classroom context, an emerging technology, already widely utilised in students’ out-of-school lives. Science educators are calling for the broadening of what constitutes a scientific text, the greater inclusion and manipulation of multi-modal representations for science students, and an increased emphasis on socio-communicative approaches to science learning. Additionally, incorporation of technology and associated means of learning, authentic to many students’ out-of-school lives, is advocated for the classroom. Student video production in science answers these calls. It achieves this while delivering unique learning benefits that add significantly to student attainment in science. Video production is playing a greater role in acquisition and dissemination of science knowledge. The use of video production in science and society would seem destined to increase exponentially. This study has investigated one application of the use of video production in a middle years science class, however the implications for further research are vast as the technology develops, the societal usage increases, and the scientific applications of video production become more powerful and widespread.

The reduction in visual performance typically found in keratoconic patients is believed to be associated with large magnitudes of uncorrected irregular astigmatism and higher-order aberrations (HOAs). Previous studies indicate that correcting HOAs in keratoconus patients may result in an improvement in visual performance. This thesis explores the correction of HOAs using standard sphero-cylindrical and customised aberration-controlling soft contact lenses in 22 patients with keratoconus. The findings of this work may be useful from a clinical perspective, as some keratoconic patients cannot tolerate rigid gas-permeable (RGP) contact lenses and have few alternatives, excluding surgical intervention, for vision correction. This thesis firstly describes a series of preliminary studies conducted to improve our current understanding of the HOAs manifested in keratoconus. The results of these investigations suggested that alterations in aberrations, due to changes in accommodation or variations in the pre-corneal tear film post-blink, were unlikely to hinder the correction of HOAs for keratoconic patients. Equally, it was ascertained that subjective refraction data provided significantly better visual acuity compared to objective, aberrometry-derived refractions for patients with keratoconus. The findings also show that both lower-order aberrations (LOAs) and HOAs displayed a larger degree of variability in keratoconic eyes compared to those previously reported for visually-normal subjects. Furthermore, significant increases in 3rd-order coma root mean square aberrations were found after temporarily suspending RGP contact lens wear for 16 keratoconic patients. The results of two clinical studies suggested that standard sphero-cylindrical soft lenses can, to some extent, mask HOAs in keratoconic patients; however, the visual performances achieved were found to be poorer compared to RGP lenses. Equally, the results showed that RGP lenses provide superior visual performances compared to customised, aberration-controlling lenses, in spite of the customised lenses providing comparable reductions in uncorrected HOAs. The inducement of superfluous HOAs and LOAs, through customised contact lens translations and rotations, were modelled using MatLab (version 7.6.0.324; The Mathworks, Natick, MA, US). The results confirmed that minimising the decentration of aberration-controlling contact lenses, to less than 5 degrees of rotation and less than 0.50 mm of translation, will help to achieve an optimal correction of HOAs. However, more stringent criteria were required for LOAs, where rotational displacements should be reduced to less than 3 degrees and translational displacements should be limited to less than 0.10 mm. In conclusion, the correction of HOAs for patients with keratoconus is possible using customised, aberration-controlling soft contact lenses; however, several factors will govern their success, including the repeatability and accuracy of HOA measurements for these irregular corneas, and the stability of the customised lenses on-eye.

The presence in state standards of the Taxonomy of Educational Objectives: Cognitive Domain (referred to Bloom 1 in this study) and A Taxonomy of Learning, Teaching, and Assessing (referred to as Bloom 2 in this study) was examined in this qualitative investigation. Standards for the English language arts eighth grade curriculum were chosen for examination in order to maximize the opportunity for all Bloom levels to appear; all states have language arts standards and eighth grade is the highest grade level at which NCLB testing is mandated. The standards documents of the 36 stated that have language arts standards unique to eighth grade comprised the analyzed data source and were accessed from state education websites. Descriptive narrations of cognitive levels, benchmarks, indicators, strands, sub-strands, writers of the standards, and any and all references to Bloom 1 and Bloom 2 were investigated. Inter-coder reliability was calculated to address the major research question regarding the clarity of reference to cognitive level of the standards. The qualitative content analysis research methodology chosen to answer the study's research questions culminated in the emergence of four major themes. 1) The extent to which the state standards were classifiable according to Bloom 1 or Bloom 2 depended largely upon consonance in assumptions made by the coders regarding a presumed conditions component for the standards; state standards lack condition components specifying what learners are presented with or have access to at the time the competency stated in the standard is demonstrated. 2) Eighth grade English language arts state standards incorporate cognitive learning levels of Bloom 1 and/or Bloom 2 through the range of Bloom levels. The verb "use" was noted as the most frequent taxonomic verb appearing in the standards. 3) Only five states directly referenced Bloom 1 or Bloom 2 in the documents' introduction/overview, table of contents, document guides, acknowledgements, appendices, and/or bibliography. 4) Of the 2,566 standard statements examined, 96 percent appear to be above the lowest Bloom 1 (Knowledge) and Bloom 2 (Remember) level, employing the researcher's assumed condition component. Overall, results showed that while some states incorporate Bloom 1 and/or Bloom 2, a majority of the standards appear to be written in the lower levels of the Bloom taxonomies. The researcher suggested strategies such as collaboration, consulting, training, and surveying students, parents, teachers, administrators, state committees, and agencies on knowledge of and inclusion of the Bloom taxonomic frameworks in order to improve the clarity of the intended cognitive levels set by the state standards.

Extreme ultraviolet (XUV) frequency combs exhibit promise for enabling high-precision spectroscopic measurements of myriad chemical species for the first time. Coherent XUV radiation can be generated through high harmonic generation (HHG) in femtosecond enhancement cavities. HHG efficiency is limited by nonlinear phase shifts induced by residual intracavity plasma. The goal of this work is to gain insight regarding plasma dynamics in order to allay the detrimental effects of plasma interactions. Our approach is to conduct simulations of cavity pump-probe experiments by probing with higher-order transverse modes. We propose methods for estimating spatial plasma profiles, gas jet velocities, and the plasma recombination coefficient based on measurements of plasma-induced phase shifts. Beam distortion due to plasma interaction is analyzed and used as another reference for plasma dynamics.

It is well known that quad-ridged horn antennas in general have impedance and radiation characteristics that are significantly worse than that of their double-ridged counterparts. Normally a voltage standing wave ratio (VSWR) of 3 over the operational bandwidth is used for the design specification of quad-ridged horn antennas. The bandwidth of operation is severely restricted due to the excitation of higher order modes in the co-axial to waveguide transition of the antenna. The higher order modes cause a break-up in the radiation pattern of the antenna and large dips in the boresight gain. The performance of the quad-ridged horn antenna with pyramidal sidewalls is improved by separating the antenna into the transition and flared horn sections, and optimizing these sections individually. It is shown that a transition section with a pyramidal cavity and steps, and a flared horn section with an exponential profile with a circular segment for the ridges deliver the best performance. These configurations for the transition and flared horn sections are combined in the complete antenna. The optimized antenna has a 12.5:1 operational bandwidth with improved performance in terms of the VSWR, the coupling between the ports and the boresight gain. A prototype of this antenna is manufactured. Good agreement between the measured and simulated performance is achieved. / Dissertation (MEng)--University of Pretoria, 2013. / gm2014 / Electrical, Electronic and Computer Engineering / unrestricted

Doctor of Philosophy / Department of Physics / Zenghu Chang / It is still a dream to image the dynamics of electrons in atoms and molecules experimentally. This is due to the fact that such motion takes place in an ultra-short time scale; for example, an electron moves around the Bohr orbit in about 150-as (1 as = 10 -18 s), and pulses much shorter than this limit are not currently available to probe such fast dynamics. In recent years, an isolated single attosecond pulse has been produced by extracting the cutoff of harmonic spectrum driven by a laser pulse as short as ~ 5fs (1fs =10-15 s). But, these pulses are still too long in order to make the dream come true. Here, we study the possibility of generation of a much shorter and wavelength tunable single attosecond pulse by using polarization gating. In the experiment, we compressed ~30fs pulses from the laser amplifier down to ~6fs and characterized them. These linearly polarized pulses were converted to ellipticity varying pulses, and by exploiting the property of the strong dependence of the harmonic signal with the ellipticity of the laser, an XUV supercontinuum was produced in the harmonic spectrum which could support 60-as pulses. The bandwidth of such a supercontinuum, and therefore the duration of the attosecond pulses, is limited mainly by the currently available energy of the driving laser pulses at few cycle limits. In this project, we present an approach which allowed us to scale up the energy of such pulses by a factor of 1.5 in “Hollow Core Fiber / Chirped Mirrors Compressor”. Finally, in order to temporarily characterize the attosecond pulses we designed and built an “Attosecond Streak Camera”. Most of such cameras to date are limited to measuring a 1 dimensional energy spectrum and have only a few degrees of acceptance angle. Our camera is capable of measuring 2d momentum of the photoelectrons with large acceptance angle, for example ~ 65o at the photoelectron of energy ~15 eV. Recently, we observed the sidebands in addition to the main peaks in their laser assisted XUV photoelectron spectrum. The single attosecond pulses, after being characterized with this high speed camera, can be used to explore the dynamics of electrons at the attosecond scale.

No description available.

Hybrid is a two-level logical framework that supports higher-order abstract syntax (HOAS), where a specification logic (SL) extends the class of object logics (OLs) we can reason about. We develop a new Hybrid SL and formalize its metatheory, proving weakening, contraction, exchange, and cut admissibility; results that greatly simplify reasoning about OLs in systems providing HOAS. The SL is a sequent calculus defined as an inductive type in Coq and we prove properties by structural induction over SL sequents. We also present a generalized SL and metatheory statement, allowing us to prove many cases of such theorems in a general way and understand how to identify and prove the difficult cases. We make a concrete and measurable improvement to Hybrid with the new SL formalization and provide a technique for abstracting such proofs, leading to a condensed presentation, greater understanding, and a generalization that may be instantiated to other logics.

The goal of this thesis is to explore some variations of neural networks. The thesis is mainly split into two parts: a variation of the shaping functions in neural networks and a variation of learning rules in neural networks. In the first part, we mainly investigate polynomial perceptrons - a perceptron with a polynomial shaping function instead of a linear one. We prove the polynomial perceptron convergence theorem and illustrate the notion by showing that a higher order perceptron can learn the XOR function through empirical experiments with implementation. In the second part, we propose three models (SMLP, SA, SA2) for stream learning and anomaly detection in streams. The main technique allowing these models to perform at a level comparable to the state-of-the-art algorithms in stream learning is the learning rule used. We employ mini-batch gradient descent algorithm and stochastic gradient descent algorithm to speed up the models. In addition, the use of parallel processing with multi-threads makes the proposed methods highly efficient in dealing with streaming data. Our analysis shows that all models have linear runtime and constant memory requirement. We also demonstrate empirically that the proposed methods feature high detection rate, low false alarm rate, and fast response. The paper on the first two models (SMLP, SA) is published in the 29th Canadian AI Conference and won the best paper award. The invited journal paper on the third model (SA2) for Computational Intelligence is under peer review.

Automated Theorem Provers (ATP) are software programs which carry out inferences over logico-mathematical systems, often with the goal of finding proofs to some given theorem. ATP systems are enormously powerful computer programs, capable of solving immensely difficult problems. Currently, many automated theorem provers exist like E, vampire, SPASS, ACL2, Coq etc. However, all the available theorem provers have some common problems: (1) Current ATP systems tend not to try to find proofs entirely on their own. They need help from human experts to supply lemmas, guide the proof, etc. (2) There is not a single proof system available which provides fully automated platforms for both First Order Logic (FOL) and other Higher Order Logic (HOL). (3) Finally, current proof systems do not have an easy way to quickly deploy and reason over new logical systems, which a logic researcher may want to test. In response to these problems, I introduce the MATR framework. MATR is a platform-independent, codelet-based (independently operating processes) proof system with an easy-to-use Graphical User Interface (GUI), where multiple codelets can be selected based on the formal system desired. MATR provides a platform for different proof strategies like deduction and backward reasoning, along with different formal systems such as non-classical logics. It enables users to design their own proof system by selecting from the list of codelets without needing to write an ATP from scratch.