3D Particle Tracking Velocimetry Method: Advances and Error Analysis

A full three-dimensional particle tracking system was developed and tested. By using three separate CCDs placed at the vertices of an equilateral triangle, the threedimensional location of particles can be determined. Particle locations measured at two different times can then be used to create a three-component, three-dimensional velocity field. Key developments are: the ability to accurately process overlapping particle images, offset CCDs to significantly improve effective resolution, allowance for dim particle images, and a hybrid particle tracking technique ideal for three-dimensional flows when only two sets of images exist. An in-depth theoretical error analysis was performed which gives the important sources of error and their effect on the overall system. This error analysis was verified through a series of experiments, which utilized a test target with 100 small dots per square inch. For displacements of 2.54mm the mean errors were less than 2% and the 90% confidence limits were less than 5.2 μm in the plane perpendicular to the camera axis, and 66 μm in the direction of the camera axis. The system was used for flow measurements around a delta wing at an angle of attack. These measurements show the successful implementation of the system for three-dimensional flow velocimetry

On imploding cylindrical and spherical shock waves in a perfect gas

The problem of a cylindrically or spherically imploding and reflecting shock wave in a flow initially at rest is studied without the use of the strong-shock approximation. Dimensional arguments are first used to show that this flow admits a general solution where an infinitesimally weak shock from infinity strengthens as it converges towards the origin. For a perfect-gas equation of state, this solution depends only on the dimensionality of the flow and on the ratio of specific heats. The Guderley power-law result can then be interpreted as the leading-order, strong-shock approximation, valid near the origin at the implosion centre. We improve the Guderley solution by adding two further terms in the series expansion solution for both the incoming and the reflected shock waves. A series expansion, valid where the shock is still weak and very far from the origin, is also constructed. With an appropriate change of variables and using the exact shock-jump conditions, a numerical, characteristics-based solution is obtained describing the general shock motion from almost infinity to very close to the reflection point. Comparisons are made between the series expansions, the characteristics solution, and the results obtained using an Euler solver. These show that the addition of two terms to the Guderley solution significantly extends the range of validity of the strong-shock series expansion

A Historical Analysis Of The Post-Apartheid Dispensation Education In South Africa (1994-2011)

The period 1994-2011 introduced a new historical era for school education in South Africa. Outcomes-based Education (OBE) was introduced and was controversial from the outset for educators and policymakers alike. The reason given for the implementation of OBE was to move away from the apartheid curriculum and to address skills, knowledge and values. However, there were various shortcomings and many implementation problems that had to be addressed. Educators perceived the OBE approach to education as so problematic that it has now, finally, had to be scrapped. At this stage, the National Senior Certificate (NSC) is the exit point for school leavers and serves as a benchmark for tertiary education. Standardization is the tool used to make adjustments to Grade 12 results to correct fluctuations in performance that are the results of factors within the examination processes rather than the knowledge and abilities of candidates but this has a direct impact on the results of candidates. International benchmarking tests (e.g. TIMSS) have been introduced at the end of Grades 3, 6, and 9 to test the competency of learners in Mathematics and Science. Compared to other participating countries, the outcome for South African learners was exceedingly poor and this is seen as a reason for serious concern

Description of a new species of Afroedura (Loveridge) (Reptilia: Gekkonidae) from the south-western Cape

A new gekkonid species, Afroedura hawequensis, is described from the south-western Cape (South Africa). The three species groups recognized in the genus are discussed

Present-Day Dillemas And Challenges Of The South African Tertiary System

The Education White Paper 3 on Higher Education aimed to transform the higher education system. Change within tertiary education included adjusting the size and shape of institutions, the meaning of autonomy and accountability, the nature of higher education, the character of student demographic distribution, management and governance, roles of student politics, models of delivery, the notion of higher education in terms of the relationship between free trade and public good, programme changes and the nature of the academic workplace. At this stage, transformation in higher education is leaping outwards to fulfil the criteria set by international competitiveness and related efficiency criteria that can be attributed to globalisation pressures and to deeper factors inherent in the nature of higher education, especially in terms of its resistance to change and modernization. In this regard, the tertiary higher education system in South Africa is faced with many multi-dimensional challenges that need to be addressed in this article. This includes stating whether Grade 12 results as the outcome of this exit point at school level are, internationally speaking, a reasonable predictor of first-year academic success at university. In South Africa, there is no benchmarking of the National Senior Certificate (NSC) examination; therefore, first-year students have difficulty in adapting to the university environment as they find themselves devoid of indispensable bases for the pursuit of their studies and the weakness of the level of education given at school level in a large number of instances. Furthermore, five universities were placed under administration in the 2011-2012 period because of appallingly poor levels of management, which adds extra layers of suspicion to the notion of the impact of higher education in South Africa. Many other challenges are facing the South African tertiary education system, which will be analysed and recommendations arrived at that will attempt to contribute to an enhancement of tertiary education in South Africa

3D object classification in baggage computed tomography imagery using randomised clustering forests

We investigate the feasibility of a codebook approach for the automated classification of threats in pre-segmented 3D baggage Computed Tomography (CT) security imagery. We compare the performance of five codebook models, using various combinations of sampling strategies, feature encoding techniques and classifiers, to the current state-of-the-art 3D visual cortex approach [1]. We demonstrate an improvement over the state-of-the-art both in terms of accuracy as well as processing time using a codebook constructed via randomised clustering forests [2], a dense feature sampling strategy and an SVM classifier. Correct classification rates in excess of 98% and false positive rates of less than 1%, in conjunction with a reduction of several orders of magnitude in processing time, make the proposed approach an attractive option for the automated classification of threats in security screening settings

A FRET-based method for monitoring structural transitions in protein self-organization

Proteins assemble into a variety of dynamic and functional structures. Their structural transitions are often challenging to distinguish inside cells, particularly with a high spatiotemporal resolution. Here, we present a fluorescence resonance energy transfer (FRET)-based method for continuous and high-throughput monitoring of protein self-assemblies to reveal well-resolved transient intermediate states. Intermolecular FRET with both the donor and acceptor proteins at the same target protein provides high sensitivity while retaining the advantage of straightforward ratiometric imaging. We apply this method to monitor self-assembly of three proteins. We show that the mutant Huntingtin exon1 (mHttex1) first forms less-ordered assemblies, which develop into fibril-like aggregates, and demonstrate that the chaperone protein DNAJB6b increases the critical saturation concentration of mHttex1. We also monitor the structural changes in fused in sarcoma (FUS) condensates. This method adds to the toolbox for protein self-assembly structure and kinetics determination, and implementation with native or non-native proteins can inform studies involving protein condensation or aggregation