Flood modelling using data available on the Internet

Includes bibliographical references (p. 95-102).The aim of this study was to determine if sufficient data at no charge is available on the Internet to use as input to a free and open source hydrological model for use in a flood monitoring system. As such, the monitoring system would be SensorWeb enabled. The study area is the C83A quaternary catchment (746 km2) in the Northern Free State, part of the Vaal primary catchment in South Africa

Two-dimensional quantum black holes: Numerical methods

We present details of a new numerical code designed to study the formation and evaporation of 2-dimensional black holes within the CGHS model. We explain several elements of the scheme that are crucial to resolve the late-time behavior of the spacetime, including regularization of the field variables, compactification of the coordinates, the algebraic form of the discretized equations of motion, and the use of a modified Richardson extrapolation scheme to achieve high-order convergence. Physical interpretation of our results will be discussed in detail elsewhere

Aligning school discipline with the best interests of the child: Some deficits in the legislative framework

The best-interest-of-the-child concept should guide the legislative framework with regard to the approach followed as well as the disciplinary processes used in schools. Currently schools revert mostly to a retributive and adversarial approach to discipline that is not compatible with the best-interests-of-the-child standard. In this article, the provisions of section 8 of the Schools Act are scrutinised and it is concluded that these provisions are supporting an adversarial and punitive approach to school discipline. This is evident from the lack of prescriptions ensuring that sanctions serve the best interest of children, the insufficient provision for support measures and structures for counselling, the undue focus on the best interests of the transgressor and the lack of guidance concerning the appointment of an intermediary. The introduction of restorative discipline as an alternative approach to discipline is recommended. The latter approach is recommended, because it is submitted that amendments to the existing legislative provisions would not address the key objection to the legislative framework namely its retributive and adversarial character

Die effek van die regulering van maksimum werkure op werknemers se grondwetlike reg op gelykheid

The paper examines the effect of the provisons regulating maximum working hours, with reference to the principle of equality entrenched in section 9 of the Constitution of the Republic of South Africa, 1996. Section 9(1) read with section 10(1) of the Basic Conditions of Employment Act 75/1997 has the effect that, subject to certain exceptions, employees are not allowed to work for the same employer for more than 55 hours per week. This does not prevent employees from working longer hours in total for different employers, an option that entails clear disadvantages. As a result of the adverse effect of past discrimination, black people, women and people on low socio-economic levels are disproportionately more unfavourably positioned in respect of levels of income, occupational status, financial ability and, consequentially, opportunities for promotion and improvement. This disadvantage often creates a need to work longer hours, specifically for the same employer. An application of the test developed in Harksen v Lane NO leads to a conclusion that the provisions referred to constitute unfair discrimination in terms of section 9 of the Constitution. The provisions also fail the proportionality test of section 36 of the Constitution

Ninja data analysis with a detection pipeline based on the Hilbert-Huang Transform

The Ninja data analysis challenge allowed the study of the sensitivity of data analysis pipelines to binary black hole numerical relativity waveforms in simulated Gaussian noise at the design level of the LIGO observatory and the VIRGO observatory. We analyzed NINJA data with a pipeline based on the Hilbert Huang Transform, utilizing a detection stage and a characterization stage: detection is performed by triggering on excess instantaneous power, characterization is performed by displaying the kernel density enhanced (KD) time-frequency trace of the signal. Using the simulated data based on the two LIGO detectors, we were able to detect 77 signals out of 126 above SNR 5 in coincidence, with 43 missed events characterized by signal to noise ratio SNR less than 10. Characterization of the detected signals revealed the merger part of the waveform in high time and frequency resolution, free from time-frequency uncertainty. We estimated the timelag of the signals between the detectors based on the optimal overlap of the individual KD time-frequency maps, yielding estimates accurate within a fraction of a millisecond for half of the events. A coherent addition of the data sets according to the estimated timelag eventually was used in a characterization of the event.Comment: Accepted for publication in CQG, special issue NRDA proceedings 200

The sampling theorem based methodology for harmonics analysis

This paper investigates the validity of the sampling theorem in the analysis of supply side line current harmonics as applied to 6-pulse AC-DC thyristor converters. The common pattern of the percentage harmonic factor, for the converter characteristic harmonic current, per incremental change of the thyristor firing angle is used as the basis of the study. The RMS values of the peak amplitudes of the characteristic harmonic currents induced in the input-phase of the converter supplying a DC motor are described in terms of the sampling theorem equations and further evaluated in terms of their respective individual harmonic contributions as the thyristor firing angle is changed. The MatLab/Simulink package is also employed to simulate the forward drive speed control operation of a DC motor using the 6-pulse AC-DC thyristor converter. However the percentage harmonic factor trends observed in the sampling theorem method appear to be generally increasing which is in contradiction to the MatLab/Simulink produced trends

Comparisons of binary black hole merger waveforms

This a particularly exciting time for gravitational wave physics. Ground-based gravitational wave detectors are now operating at a sensitivity such that gravitational radiation may soon be directly detected, and recently several groups have independently made significant breakthroughs that have finally enabled numerical relativists to solve the Einstein field equations for coalescing black-hole binaries, a key source of gravitational radiation. The numerical relativity community is now in the position to begin providing simulated merger waveforms for use by the data analysis community, and it is therefore very important that we provide ways to validate the results produced by various numerical approaches. Here, we present a simple comparison of the waveforms produced by two very different, but equally successful approaches--the generalized harmonic gauge and the moving puncture methods. We compare waveforms of equal-mass black hole mergers with minimal or vanishing spins. The results show exceptional agreement for the final burst of radiation, with some differences attributable to small spins on the black holes in one case.Comment: Revtex 4, 5 pages. Published versio

Effective leadership considering emotional intelligence in a leadership environment.

The primary objective is to establish whether a potential trend exists between effective leadership and emotional intelligence (EI). This research also investigates whether possible trends exist between leadership and emotional intelligence in terms of the leadership styles: transformational or transactional leadership. Insight is also gained into whether male or female student leaders practice either transformation or transactional leadership styles. The sample was identified as the student leaders at the University of Johannesburg's Auckland Park Kingsway campus. The sample ultimately included 123 respondents for all the committees in the institution, resulting in a very positive response rate for data analysis. The findings revealed that there was insufficient evidence to support the objective that specific trends exist between leadership effectiveness when considering emotional intelligence or whether emotional intelligences relates more strongly with a transformational or transactional leadership style. However relevant relationships between female respondents and the transformational leadership style could be established

Black Hole Mergers and Unstable Circular Orbits

We describe recent numerical simulations of the merger of a class of equal mass, non-spinning, eccentric binary black hole systems in general relativity. We show that with appropriate fine-tuning of the initial conditions to a region of parameter space we denote the threshold of immediate merger, the binary enters a phase of close interaction in a near-circular orbit, stays there for an amount of time proportional to logarithmic distance from the threshold in parameter space, then either separates or merges to form a single Kerr black hole. To gain a better understanding of this phenomena we study an analogous problem in the evolution of equatorial geodesics about a central Kerr black hole. A similar threshold of capture exists for appropriate classes of initial conditions, and tuning to threshold the geodesics approach one of the unstable circular geodesics of the Kerr spacetime. Remarkably, with a natural mapping of the parameters of the geodesic to that of the equal mass system, the scaling exponent describing the whirl phase of each system turns out to be quite similar. Armed with this lone piece of evidence that an approximate correspondence might exist between near-threshold evolution of geodesics and generic binary mergers, we illustrate how this information can be used to estimate the cross section and energy emitted in the ultra relativistic black hole scattering problem. This could eventually be of use in providing estimates for the related problem of parton collisions at the Large Hadron Collider in extra dimension scenarios where black holes are produced.Comment: 16 pages, 12 figures; updated to coincide with journal versio