Theorising South Africa's foreign policy: The case of Latin America

African Studies Seminar series. Paper presented 13 May, 1985. Not to be quoted without the Author's permissionDuring recent years local scholarship in the field of South Africa's foreign policy has tended to focus on the structure of state institutions and on the personalities of the decision makers. Whilst I do not wish to underplay the importance of monitoring the transformation occurring within the state apparatus , especially in relation to the militarization of the top layers of the bureaucracy, it is nevertheless important to draw away from an emphasis on the model of bureaucratic politics if one is to do full justice to an understanding of South Africa’s interactions with other social formations

Biomechanical evolution of the Tkachev on uneven bars in female gymnastics

The development of joint kinematics and kinetics is fundamental to the successful performance of complex flight skills in gymnastics bar routines. Biomechanical understanding of these skills can provide coaches and scientists with key information to make training safe and effective. The Tkachev is a complex and popular gymnastics skill with many different variations. Recently, a new version has been performed, which has become popular with elite female performers. This study examined the key biomechanical characteristics of this skill and contrasted these to the earlier versions reported. Elite female gymnasts (n = 5) were recorded and manually digitised using twin video cameras (50 Hz) at the 2007 World Gymnastics Championships. Three-dimensional (3D) DLT was used to reconstruct the real world coordinates. Individualised inertia characteristics were calculated and used to determine mass centre kinematics. Inverse dynamics analysis was used to calculate joint kinetics at the hips and shoulders from the known values at the toes. The results of this study showed an increased flight time and rotational capacity during the aerial phase for the toe-on Tkachev, as well as a more simple movement pattern and joint kinetic demand with single power impulses at the hips and shoulders compared with previous versions. The key finding of this study was that the toe-on version appeared to be less physically demanding than that the inward and outward techniques, and provide the opportunity to perform more complex aerial phase body positions. These results can help coaches to physically prepare their gymnasts and biomechanists in terms of understanding the demands of these skills

An Investigation of a Mixer-Ejector Nozzle for Jet Noise Reduction

An experimental study is conducted assessing the performance of an ejector together with an 8:1 aspect ratio rectangular nozzle with the eventual goal of noise reduction for jet engines. Wall static pressure and Pitot probe surveys are conducted to evaluate the performance of the ejector, and sound pressure level measurements are made to assess the impact on noise radiation. It is found that addition of vortex generating tabs at the lip of the nozzle causes large increases in secondary flow entrainment. The baseline ejector (without tabs) often encounters flow resonance with accompanying tones. The tabs have the additional benefit of eliminating those tones. In most cases tried so far, pockets of high-speed fluid remain unmixed. Since jet noise scales as velocity to the eighth power, such hot spots defeat the noise reduction goal. In some cases, there is a reduction in noise amplitudes in the mid-frequency range (5-30 kHz), however, an increase occurs on the low frequency end apparently due to flow unsteadiness. This together with a high frequency noise increase caused by the tabs results in minimal reductions in the overall sound pressure level. The focus of ongoing and future efforts is to achieve sufficient mixing and desirable noise reduction while keeping the hard-ware short and lightweight

Metastability and Nucleation for the Blume-Capel Model. Different mechanisms of transition

We study metastability and nucleation for the Blume-Capel model: a ferromagnetic nearest neighbour two-dimensional lattice system with spin variables taking values in -1,0,+1. We consider large but finite volume, small fixed magnetic field h and chemical potential "lambda" in the limit of zero temperature; we analyze the first excursion from the metastable -1 configuration to the stable +1 configuration. We compute the asymptotic behaviour of the transition time and describe the typical tube of trajectories during the transition. We show that, unexpectedly, the mechanism of transition changes abruptly when the line h=2*lambda is crossed.Comment: 96 pages, 44 tex-figures, 7 postscript figure

The influence of hand positions on biomechanical injury risk factors at the wrist joint during the round-off skills in female gymnastics

The aim of this study was to examine the biomechanical injury risk factors at the wrist, including joint kinetics, kinematics and stiffness in the first and second contact limb for parallel and T-shape round-off (RO) techniques. Seven international-level female gymnasts performed 10 trials of the RO to back handspring with parallel and T-shape hand positions. Synchronised kinematic (3D motion analysis system; 247 Hz) and kinetic (two force plates; 1235 Hz) data were collected for each trial. A two-way repeated measure analysis of variance (ANOVA) assessed differences in the kinematic and kinetic parameters between the techniques for each contact limb. The main findings highlighted that in both the RO techniques, the second contact limb wrist joint is exposed to higher mechanical loads than the first contact limb demonstrated by increased axial compression force and loading rate. In the parallel technique, the second contact limb wrist joint is exposed to higher axial compression load. Differences between wrist joint kinetics highlight that the T-shape technique may potentially lead to reducing these bio-physical loads and consequently protect the second contact limb wrist joint from overload and biological failure. Highlighting the biomechanical risk factors facilitates the process of technique selection making more objective and safe

A critical assessment of UH-60 main rotor blade airfoil data

Many current comprehensive rotorcraft analyses employ lifting-line methods that require main rotor blade airfoil data, typically obtained from wind tunnel tests. In order to effectively evaluate these lifting-line methods, it is of the utmost importance to ensure that the airfoil section data are free of inaccuracies. A critical assessment of the SC1095 and SC1094R8 airfoil data used on the UH-60 main rotor blade was performed for that reason. Nine sources of wind tunnel data were examined, all of which contain SC1095 data and four of which also contain SC1094R8 data. Findings indicate that the most accurate data were generated in 1982 at the 11-Foot Wind Tunnel Facility at NASA Ames Research Center and in 1985 at the 6-inch by 22-inch transonic wind tunnel facility at Ohio State University. It has not been determined if data from these two sources are sufficiently accurate for their use in comprehensive rotorcraft analytical models of the UH-60. It is recommended that new airfoil tables be created for both airfoils using the existing data. Additional wind tunnel experimentation is also recommended to provide high quality data for correlation with these new airfoil tables

Contour map of thermal efficiency ijj

Exergy Analysis for the Performance of Solar Collectors The optimum control and performance evaluation of solar collectors are analyzed from the standpoint of exergy. The pressure drop inside the collector is introduced to the analysis using the Hottel-Whillier model. By treating the friction process as exergy loss, the optimum operating conditions are presented in a simple statement. The maximum capability of collectors is determined and expressed by a relationship among the collector parameters and the environment in which they operates. Introduction The optimum operating conditions of solar collectors have so far been investigated on the basis of collected thermal energy. The criterion generally adopted is to maximize the difference between the collected thermal energy and the required pumping power First, exergy analysis using the Hottel-Whillier model Exergy Analysis Using the Hottel-Whillier Model The properties of flat-plate solar collectors are, in general, given by the relationship among the outlet and inlet temperatures T 0 , Tj, the mass flow rate m, and insolation /, as From equation (1), instantaneous thermal efficiency, i},, defined by o'm /kg. s" 1 ) For the investigation of the optimum control and performance evaluation of solar collectors, it is sufficient to assume a constant environment for the first step. Therefore, only the instantaneous efficiency is considerd in the following discussion, and the daily efficiency is not treated. As one example, the insolation, I, and ambient temperature, T a , are fixed as 7=650 W/m 2 , r a = 300 K The stagnation temperature, T sl , is obtained by setting ij, = 0 in equation (3), as With respect to this case, r/, is depicted in Assuming that the specific heat, C P , at constant pressure is constant, A/z and As in equation Ae Eliminating T 0 by equation Next, the maximum exergy efficiency ijf ax over all of 7", and rh is considered. Expanding equations Setting equations = collector area = specific heat at constant pressure = inner diameter of absorber tube = friction factor = collector efficiency factor = heat removal factor = volumetric flow rate = solar radiation incident on the collector = absorber tube length = mass flow rate = ambient temperatur

The political economy of South-South relations: The case of South Africa and Latin America.

Many factors have inhibited the consolidation of relations between countries of the post-colonial world, the "South". This dissertation aims to explore some of these factors through focusing on a case study of the relations between South Africa and its neighbours across the South Atlantic. Despite naval and commercial hegemony of the British Empire in the South Atlantic region during the nineteenth century, trade proved minimal and South Africa played a limited role in assisting the indictment of the transatlantic slave trade. It was only during the Boer War (1899-1902) that South Africa became the destination of Argentine exports in large measure: frozen beef to meet the needs of British troops. With the end of the war, a significant Boer migration to Patagonia was encouraged by the Argentine government. This community served to cement relations with South Africa up to and including the time of its repatriation in the late 1930s. Brazil's participation in World War Two alongside the Allies opened the way further for relations with South Africa and support for its position inside the new postwar United Nations Organisation. Growing links with the Afro-Asian world did not deter Brazil's military rulers - in power from 1964-85 - from encouraging trade and substantial South African investment. As right-wing military rule swept the Latin American region in the 1960s and 70s, South Africa, by now extremely isolated diplomatically, found a number of friends. Moral and military collaboration from the regimes in the Southern Cone - especially Chile - proved very welcome in Pretoria. Its adversarial relationship with Cuba in the context of regional conflict in Southern Africa also proved important. With redemocratisation in both regions the nature of the relationship will require re-examination. However, in the context of largely dormant South-South relationships, it is unlikely to expand massively under current global conditions of debt, trade competition, and commercial and cultural barriers. Utilising methodological analysis drawn from disciplines of economic history, social history, foreign policy analysis and international political economy, this dissertation attempts to throw light on a rather neglected corner of international relations

IBE-IBE: Intent-Based Execution through Identity-Based Encryption and Auctions

This paper introduces a decentralized and leaderless sealed bid auction model for dynamic pricing of intents across blockchain networks. We leverage Multi-Party Computation (MPC) and Identity-Based Encryption (IBE) to improve pricing while ensuring fairness and decentralization. By addressing the vulnerabilities of current centralized or static pricing mechanisms, our approach fosters transparent, secure, and competitive price discovery. We further enhance the confidentiality of intents through Multi-Party Computation (MPC), Fully Homomorphic Encryption (FHE), and Trusted Execution Environments (TEE). Our novel methodology mitigates the risks of frontrunning and centralization while preserving the rapid settlement times essential to decentralized finance (DeFi)