School of Science
http://hdl.handle.net/10500/2736
2015-05-05T13:23:37ZThe production of 103Pd and 109Cd using proton irradiated tandem natAg/natAg targets
http://hdl.handle.net/10500/18501
The production of 103Pd and 109Cd using proton irradiated tandem natAg/natAg targets
Ineza, Claire
103Pd is an important therapeutic radionuclide and has recently found great interest due to its higher radiobiologic effect. 109Cd decays by electron capture and is generally used as calibration sources in industrial and medical fields. A new method for the production of 103Pd and 109Cd using the 66 MeV proton beam of iThemba LABS on a tandem natural silver target (Ag/Ag) has been developed. The tandem targets (each target with a mass of 9 g and a thickness of 3 mm) were placed in the high energy slot (62.515 MeV - 40.173 MeV) and low energy slot (38.652 MeV – 0 MeV) to produce the bulk 103Pd and 109Cd, respectively. The radiochemical separation of the Pd radionuclides (103Pd, 100Pd) and the co-produced Rh radioisotopes (mainly 101Rh and 100Rh which are produced from decay of their Pd parents) from the bulk natAg was achieved using a Chelex chelating resin column. In the preliminary studies, different size columns (3 cm x 1 cm, 11 cm x 1 cm, 13 cm x 1 cm and 16 cm x 1.5 cm) were investigated to determine the optimal column conditions for the separation. It was determined that the optimal conditions for the chemical separation was with a 13 cm x 1 cm resin column with the elution of Rh and Ag radionuclides carried out with 1 M HNO3 and the elution of Pd radionuclides with 10 M HCl. No Ag or Rh impurities were detected in the final product and the average recovery of Pd was > 96 %. This work was repeated using a ―hot‖ irradiated Ag target and the chemical processing was done in a hot cell using the same resin column conditions. The recovery of the high purity 103Pd from the irradiated natAg target was found to be > 95 %. The radiochemical separation of 109Cd from the bulk natAg target was done in two parts. In the first part, the precipitation method was used to reduce the silver into a metallic form using 30 g of Cu turnings. The resulting 109Cd filtrate was loaded onto a AG-X10 anion exchange resin column (6 cm x 1 cm). For the optimal chemical separation, the elution of Ag and Cu(II) was carried out with 2 M HCl containing H2O2 and the elution of 109Cd was accomplished with 1 M HNO3. The recovery yield of 109Cd was > 99 %.
2015-03-01T00:00:00ZA Lie symmetry analysis of the heat equation through modified one-parameter local point transformation
http://hdl.handle.net/10500/18414
A Lie symmetry analysis of the heat equation through modified one-parameter local point transformation
Adams, Conny Molatlhegi
Using a Lie symmetry group generator and a generalized form of Manale's formula
for solving second order ordinary di erential equations, we determine new symmetries
for the one and two dimensional heat equations, leading to new solutions. As
an application, we test a formula resulting from this approach on thin plate heat
conduction.
2014-08-01T00:00:00ZA Lie symmetry analysis of the Black-Scholes Merton finance model through modified local one-parameter transformations
http://hdl.handle.net/10500/18410
A Lie symmetry analysis of the Black-Scholes Merton finance model through modified local one-parameter transformations
Masebe, Tshidiso Phanuel
The thesis presents a new method of Symmetry Analysis of the Black-Scholes Merton
Finance Model through modi ed Local one-parameter transformations. We determine
the symmetries of both the one-dimensional and two-dimensional Black-Scholes
equations through a method that involves the limit of in nitesimal ! as it approaches
zero. The method is dealt with extensively in [23]. We further determine an invariant
solution using one of the symmetries in each case. We determine the transformation
of the Black-Scholes equation to heat equation through Lie equivalence transformations.
Further applications where the method is successfully applied include working out
symmetries of both a Gaussian type partial di erential equation and that of a di erential
equation model of epidemiology of HIV and AIDS. We use the new method to
determine the symmetries and calculate invariant solutions for operators providing
them.
2014-09-01T00:00:00ZDeep space radiations-like effects on VO2 smart nano-coatings for heat management in small satelittes
http://hdl.handle.net/10500/18408
Deep space radiations-like effects on VO2 smart nano-coatings for heat management in small satelittes
Mathevula, Langutani Eulenda
Thermal control in spacecraft will be increasingly important as the spacecraft grows smaller and more compact. Such spacecraft with low thermal mass will have to be designed to retain or reject heat more efficiently. The passive smart radiation device (SRD) is a new type of thermal control material for spacecraft. Current space thermal control systems require heaters with an additional power penalty to maintain spacecraft temperatures during cold swings. Because its emissivity can be changed without electrical instruments or mechanical part, the use of SRD decreases the request of spacecraft power budget. The (SRD) based on VO2 films is one of the most important structures of the functional thermal control surface, being lighter, more advanced and without a moving devices. A large portion of the heat exchange between an object in space and the environment is performed throughout radiation, which is in turn determined by the object surface properties. The modulation device is coated on the spacecraft surface and thus provides a thermal window that can adapt to the changing conditions in orbit.
VO2 is well known to have a temperature driven metal to insulator transition ≈ 68ᴼC accompanying a transformation of crystallographic structure, from monoclinic (M-phase, semiconductor) at temperature below 68ᴼC to tetragonal (R-phase, metal) at temperature above 68ᴼC. This transition temperature is accompanied by an increase of infrared reflectivity and a decrease of infrared emissivity with increasing temperature. This flexibility makes VO2 potentially interesting for optical, electrical, and electro-optical switches devices, and as window for energy efficiency buildings applications. This study reports on effect of thickness on VO2 as well as the effect of proton irradiation on VO2 for active smart radiation device (SRD) application. VO2 was deposited on mica by Pulsed laser deposition techniques. The thickness of the film was varied by varying the deposition time. To characterize VO2 the following techniques were performed: XRD, AFM, SEM, TEM, XPS, RBS, RAMAN and transport measurements for optical properties. The effect of proton irradiation was observed using the SEM, where the change in structure, from crystal grains to rods, was observed.
2014-01-01T00:00:00Z