This thesis includes a description of modifications of the Hilger atomic absorption apparatus, which was used for most of the work. These modifications were restricted to the atomiser and burner, which were replaced by a modified "Eel" flame. photometer atomiser-burner and resulted in improved sensitivity and instrumental stability for the atomic absorption of magnesium. A comparison of the performance of this unit with that of the unmodified Hilger apparatus is given. A "Handigas" butane-propane mixture)-air flame was used for most of this work, but a coal-gas-air flame was also studied and found to give slightly greater sensitivity. The method was found to be subject to interference from many elements. Strontium salts, employed as releasing agents to overcome the effect of other elements, were not completely effective as milligram amounts of several elements interfered even when strontium was present. Among the more serious interfering elements are: aluminium, iron, manganese and zirconium (less than 20 p.p.m. interfere); the alkali and alkaline earth metal salts (more than 200-500 p.p.m. interfere); phosphate (more than 100 p.p.m. P₂0₅ uranium (more than 4,000 p.p.m.); arsenate and vanadate. An attempt is made to explain the mechanism of some of these interfering effects. A combination of strontium salt and acetyl acetone was found to over-come the effects of small amounts of several elements that form complexes with acetyl acetone (e.g. iron and aluminium) far more effectively than strontium alone. Larger amounts of many interfering elements are removed by a solvent extraction procedure employing acetyl acetone and chloroform. Elements which cannot be removed by this means may be separated by anion-exchange, volatilisation, electrolysis or precipitation. A spiking technique, which compensates JT/GB for the effects of small amounts of interfering elements, is described and enables many samples to be analysed without prior separations. The method described has good sensitivity (the limit of determination is approximately 1 microgram of magnesium in 50 ml. of solution). It has been applied to the analysis of clay samples, iron ore, limestone and uranium metal, oxides and processing solutions. The coefficient of variation of the method was determined using two clay samples and results of 2.0 and 4.6 percent, at magnesium oxide concentrations of 0.65 and 0.22 percent respectively, wore obtained. The speed of the method compares favourably with others described for the determination of microgram amounts of magnesium, but increases if large amounts of interfering elements are present.

A glass electrode is described which is capable of detecting photosynthetic CO₂ uptake by monitoring the concentration of CO₂ dissolved in a small drop of algal suspension. Consideration of current theory suggests that transients should occur in the rate of CO₂ uptake which are similar to but distinct from those observed in O₂ evolution rate. These transients should be most readily observed when cells are illuminated alternately with wavelengths of 650 nm and 705 mn. The preliminary results show that C0₂ uptake by photosynthesis can be monitored by this apparatus. Although transients were not observed, this may be due to the rather low sensitivity. There is a discussion of shortcomings of the apparatus, and of improvements necessary before transients can be observed. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

A significant improvement in magnetic probe measurements has been achieved by developing a 3-coil magnetic probe which partially corrects for the boundary error, i.e. for the error caused by an exclusion of the plasma current from the space occupied by the probe. The spatial resolution C of the three coil probe is roughly one-half of the probe radius, a. For current distributions which vary slowly with distance (scale length, ƛ ) it is shown that the fractional error in the magnetic field is 0.2 (C/ ƛ)². For a conventional probe the error is at least four times as large. Also it has been shown that spurious signals arising from poor probe geometry (and which often obscure the signals produced by the measured magnetic fields themselves) can be eliminated by making use of the symmetry of the discharge fields. Measurements have been made on a Z-pinch discharge which confirm the claimed 3-coil probe performance by revealing a "fine" structure of the current distribution in helium in the filling pressure range 0.5 to 4 Torr. The measurements are presented in the form of a catalogue of the spatial distribution of magnetic field and the current density for a Z-pinch discharge in He and Ar. Using the probe measurements a qualitative model of the collapse of the current sheet for 4 Torr in He is developed which differs from previous models. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

M.Tech. (Electrical Engineering) / The challenges faced by modern industrial robots and robots in general are increasing in cornplexity. A modern robot can be defined as a technological system. capable of replacing or assisting man in carrying out a variety of physical tasks. Thus the implementation of advanced technology in the field of industrial robotics poses different challenges to those faced by engineers in other fields. The reason for this lies mainly in the fact that robots have to be be able to interact with their environment in some intelligent way. For the robot to be able to accomplish this. it must be able to obtain information about its immediate surroundings. and/or its position in the surroundings. In the case of industrial or other stationary robots. the knowledge about its surroundings are of less importance than its own position and the position of the relevant workpieces in the work space. Traditionally the position of a robot arm is measured using position encoders mounted at the joints of the robot arm. The combination of information obtained from these sensors gives the position of the endpoint of the arm. To ensure that the encoder positions accurately reflect the actual position of the arm. the arms have to be rigid, resulting in a heavy. bulky and costly system. If it were possible to determine the endpoint of a robot arm without using the joints of the arm as reference points, it would be possible to design more flexible robot arms. resulting in less costly and more maneuverable systems. Various solutions were considered for this measurement problem and from these it was decided to investigate the use of inertial measurement technology to determine the endpoint position of a flexible robot arm. To test the use of gyroscopes as feedback sensors in the position control of a flexible robot arm. a small low cost robot arm was developed. The design was based on an articulated robot arm with three degrees of freedom (DOF). The system was designed to be fitted with a flexible arm segment to evaluate the gyroscope-based feedback system. The system was further fitted with traditional position sensors to be used as the benchmark against which the gyroscope-based control system was to be compared. Making use of the traditional position sensors the endpoint of the arm can be accurately placed in a space of :3mm x 4mm x 1mni. When the robot was fitted with the flexible arm segment the gyroscopes were able to measure movement of the flexible ann. which the traditional sensors could not detect. Using the gyroscopes as position feedback. the robot was able to track the potentiometer position within 0.19° under dynamic conditions, but under stationary conditions. the error was 6.50 • Based on the results obtained. it was concluded that the displacement of a robot arm segment can be determined using inertial measurement technology. The low cost sensors used proved the concept. but for reliable operation. higher accuracy sensors would be required aided with information obtained from other sensors. i.e, potentiometers resolvers or other absolute encoders.

The purpose of this study is to investigate the phenomenon of repression and to study its relationship to optimism/pessimism as measured by a subjective and an objective measuring instrument.

An anatomical and physiological background to the heart as a pump, followed by a description of the causes and results of cardiogenic shock is given. A survey of the achievements of other researchers in this field is included. The design of a system for controlling and monitoring the Intra-Aortic Balloon Pump is described. A narrow band-pass filter is used to reduce noise and limit the input to the detector to the spectrum within which the R-wave of an ECG signal lies. A safety circuit to prevent the heart pumping against an inflated balloon is incorporated. History of the 8 secs preceding any instant is available. A description of the medical tests carried out so far is given.

This master thesis put its focus on analysis that is based on the creation of complaints in the filed of the construction company that has been used for this research. The researched company core business activities lie in the construction and reconstruction of the roofs. This analysis is based on the comparison of already established procedures and consequently their actual execution. The shortcomings that were found in the analytical part of this research papers, will be used as suggestions that ought to improve the current situation of the researched company.

This dissertation focuses on the Organisation for Economic Co-operation and Development ('OECD') transfer pricing methods and its application to Multinational Enterprise ('MNE') groups in the financial sector. This study examines whether the OECD's Base Erosion and Profit Shifting ('BEPS') Action Plan 9 is an appropriate framework for MNE groups in the banking sector or whether it creates further challenges. Additionally, the dissertation scrutinises MNE groups in the financial sector that are involved in the business of global trading of financial instruments. It further explores the functions of a global trading entity, the arm's length principle and the OECD BEPS Action Plan 9. This dissertation concludes that the global trading of financial instruments using the integrated trading model is challenged when the OECD traditional transfer pricing methods are applied. Multinational financial institution groups in the banking sector that are involved in the business of global trading of financial instruments are subject to rigid regulations. Furthermore, the report concludes that these rigid regulations mitigate some of the complications that arise when applying the OECD BEPS Action Plan 9. Taxing authorities need to focus greater attention on the global trading of financial instruments by multinational financial institutions groups. As South Africa's financial institutions expand across borders, the concerns over transfer pricing and BEPS are likely to intensify. It is therefore imperative that the South African revenue authorities prioritise the recruitment of skilled personnel in order to address the complexities posed by the global trading of financial instruments by multinational financial institution groups.

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