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A dissertation submitted in fulfillment of the requirements to the Faculty of Science, University of the Witwatersrand, Johannesburg, for the degree of Master of Science in the School of Electrical and Information Engineering, June 2019 / The objective of this study is to determine the quantity of charge transferred, in Coulombs, during the continuing current phase of natural cloud-to-ground (CG) lightning flashes over an area in Johannesburg, South Africa. Continuing current is responsible for most thermal related lightning damages such as destruction of property, electrical fires and physical human trauma. The mitigation of lightningrelated risks can be better managed through improved measurement methods of naturally occurring lightning. The application of a point-charge model used to infer charge transfer from changing electric field measurements is detailed. A flatplate antenna with an integrator is set up to record the changing electric fields from lightning flashes. These measurements, along with high-speed video footage to determine continuing current durations, are processed and charge transfer quantities are inferred. From 34 negative lightning strokes with long continuing current (i.e. > 40 ms), the quantity of charge transfer ranges from 0.3 C to 145.5 C and has a mean quantity of 18.3 C. For the 5 recorded positive strokes, the quantity of charge transfer ranges from 3.7 C to 66.6 C / NG (2020)

Balancing an air distribution system consists primarily of measuring airflow and adjusting volume control devices to get specified airflow. Flow calculation methods are not accurate enough to ensure proper balancing by duct design alone. To assure proper balancing, dampers within an air distribution system must be adjusted until design flows are met throughout the system to within + 10%. By properly balancing an air distribution system, operating costs in the system will be reduced, comfort for the occupants in the building will be increased, and the life of the HVAC equipment will be improved. Existing balancing techniques are iterative methods that require several measurements and damper adjustments. The flows and pressures are first measured, and then the dampers are adjusted to match design airflow. The flows are measured again and the measuring and adjusting process is repeated on a trial-and-error process until design flow is achieved. This iterative process is time consuming and expensive. The proposed new balancing technique is to use a computer program that, based on a few measurements, determines damper adjustments that will achieve design airflow throughout the system. Each terminal damper is adjusted only once to a specified flowrate that is determined by the computer program, making the balancing process quicker and less expensive. No iteration is required. / Master of Science

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