In this work, Poly (diallyldimethylammonium) chloride - (PDDA) was used as a base layer for developing colloid displacement lithography platforms for sensor applications. Previous work shows that glass coated with PDDA and exposed to gold acts as a good platform for colloid displacement lithography. However, for actual sensor applications, electrical isolation of individual sensor sections must be achieved. This is attempted by laying down a 40 μm stripe of PDDA on a cleaned substrate and coating that stripe with gold colloid. The size of 40 μm or less in width is set as the target to fit within the scan window of the AFM. Stripes wider than about 40 μm would be difficult to efficiently pattern with colloid displacement lithography. While the goal of 40 μm wide stripes was achieved with sufficiently diluted PDDA solution, it was found to be difficult to adsorb sufficient amounts of gold colloid on those stripes before the stripes were lost from the glass substrate. Further, electroless deposition was found to produce only a small amount of gold on the PDDA surface without colloid nucleation sites being present.

The main objective of the study was to determine the risk(s) associated with lockout/tagout of hazardous energy and propose a new LOTO procedure which tracks the implementation of LOTO to mitigate against identified risks as a basis for promotion of safety. The study focuses on electrical personnel working in PHCN. Only electrical accident risks are examined, not other types of risk e.g. mechanical, chemical, and nuclear. To gather material for this study, a questionnaire was distributed amongst electrical workers in PHCN and their supervisors were interviewed. Relevant literature and publications were studied as reference. According to electrical personnel experience, electrocution, arc flash, arc blast, burns and lockout and tagout of the wrong electrical circuit are seen as the biggest electrical safety risk with regards to LOTO of hazardous energy. The research reveals new information about electrical accident risks. This information is used to create a procedure for tracking LOTO of hazardous energy. The procedure can be utilized in the mitigation of electrical risks and promotion of / Thesis (MIng (Development and Management Engineering))--North-West University, Potchefstroom Campus, 2013.

The main objective of the study was to determine the risk(s) associated with lockout/tagout of hazardous energy and propose a new LOTO procedure which tracks the implementation of LOTO to mitigate against identified risks as a basis for promotion of safety. The study focuses on electrical personnel working in PHCN. Only electrical accident risks are examined, not other types of risk e.g. mechanical, chemical, and nuclear. To gather material for this study, a questionnaire was distributed amongst electrical workers in PHCN and their supervisors were interviewed. Relevant literature and publications were studied as reference. According to electrical personnel experience, electrocution, arc flash, arc blast, burns and lockout and tagout of the wrong electrical circuit are seen as the biggest electrical safety risk with regards to LOTO of hazardous energy. The research reveals new information about electrical accident risks. This information is used to create a procedure for tracking LOTO of hazardous energy. The procedure can be utilized in the mitigation of electrical risks and promotion of / Thesis (MIng (Development and Management Engineering))--North-West University, Potchefstroom Campus, 2013.

Electromagnetic effects of lightning currents during a direct hit to tall communication towers, other instrumented towers and chimneys can be hazardous to associated cables, as well as, electrical and electronics systems. The standard practice in telecommunication and other related fields is to bond the cable sheath to the tower and ground connection is made before it enters the base station. However, in some specific cases when power, signal and data logging cables are to be supported on the same tower, isolation of power cables is demanded. In a totally different situation, attempts are also made to have a dedicated isolated down conductor. A critical review of the situation demanded a more quantitative answer to the following questions: (i) whether it is possible to electrically isolate a dedicated down conductor, (ii) is it possible to electrically isolate the cables and their terminal equipment both mounted on towers serving as down conductor and if so, what will be the nature of current induced in the cables and (iii) as per the standard practice, if the cable sheaths are connected to the tower/structure, what will be the nature of the current shared by them. Addressing these important issues formed the scope of the present work. For the tall structures considered in this work, for the critical time periods, wave nature of the current dominates. This called for electromagnetic modeling covering Transverse Magnetic (TM) mode of the wave propagation. Owing to the complex geometrical features involved with the problem, both experiments on electromagnetically scaled laboratory models, as well as, theoretical simulation is attempted. An electromagnetically scaled laboratory model is employed for the time domain experimental investigation. This approach, which has been validated earlier, is further scrutinized to ensure its adequacy. In order to achieve generality and noting the fact that the associated parameters are rather difficult to be varied in the experimentation, theoretical investigation is also employed. For this, both NEC-2, as well as, an in-house thin wire time domain code developed for this work is employed. NEC-2 could handle multi-wire multi-radius junctions, while in-house time domain code could handle proximity and non-cylindrical shapes encountered with tower lattice elements. The investigation of induction to isolated cables on simple down conductors and towers is considered first. The induced current is shown to be bipolar oscillatory with the period of oscillation governed by the length of the cable. It is shown that the level of induction for good earth termination is below 5 – 10 % while that with moderate inductance in the earth termination can enhance the induction to higher levels. The level of induction is shown to be not critically dependent on the length of the cable, gap between cable and down conductor/tower. When multiple cables are mounted, they seem to influence each other and individually carry currents of lower amplitude. Also, the effect of shape and proximity of the tower lattice elements on induction is investigated. If the cable is housed inside a metallic tray, the amplitude of induced current is shown to be quite small. Subsequently, the evaluation of electrical stress between the isolated down conductor on tower and simplified representation of the structure is considered. A suitable definition of the electric stress for the wave regime is evolved and then it is shown that, at present, the voltage difference defined by the path integral of electric field across shortest path between the two entities is the best indicator for the stress. The electrical stress in the case of isolated down conductor on tower, as well as, down conductor with isolated cable is shown to reach very dangerous levels. On the other hand, the stress on the isolated cables on towers also serving as down conductors is shown to be relatively moderate. Interestingly, it is shown that the electrical stress and the voltage difference is dependent on the gap and for the critical time period, can be much lower than that calculated as a product of equivalent tower surge impedance and the stroke current, even before the arrival of ground end reflections. Finally, the current shared by cables connected to the down conductor is investigated. For the case of simple cylindrical down conductor with cable connected to it at the top, it is shown that the amount of current shared by the cable is not dependent on its length and the relative radii (cross section) have only a weak influence. For the case with down conductor formed by L and + angles, it is shown that the placement of cable at their interior corner can reduce the initial current shared by the cable. In order to model best possible situation with towers, experiments are conducted with cable inside an aluminum pipe. Even in this case, cable current builds up with successive reflections to become comparable with the current through the pipe itself. Subsequent investigation with 1:40 and 1:20 tower models lead to several interesting observations. Cables running along leg/face of the tower whether placed inside or outside the tower, always shares good amount of current. Further, frequent bonding of the sheath to the tower increases the current shared by the cable. Cable when housed in a metallic tray shares less than 50% of the current shared without the tray. Even though a complete quantification is not to be achieved in this work, it has made a good beginning with some significant contribution towards lightning protection issues pertaining to tall towers and structures.