Ruaan Pelzer

A new model to estimate Bolus Insulin Need

BACKGROUND Patients with type 1 diabetes usually use the carbohydrate (CHO) counting method to establish their bolus insulin need. However, most still struggle with blood glucose control. We believe that for good control their insulin requirements should strive to mimic the insulin secretion of those without diabetes. The objective here is to develop, from first principles, a better model than the CHO counting model for calculating the bolus insulin need of subjects without diabetes. Such a model may also provide better blood glucose control for patients with type 1 diabetes. This will be investigated in a future article. METHODS Equations for metabolism of CHO and for insulin response were derived from first principles. Clinical trials were used to verify these models. The final results--namely, the new bolus insulin requirement equations--were verified using clinical trials by other researchers (Wolever and co-workers). Their methods used are described in their articles given in the list of references. RESULTS The postprandial insulin secretion relationships resulted in an average Pearson R(2) of 0.807 (for the new method) versus the old methods R(2) of 0.562 (CHO counting). CONCLUSIONS The newly derived equation provides a better approximation than the CHO counting method of insulin secretion due to metabolized blood glucose energy from ingested carbohydrates for those without diabetes. We believe that insulin dosage requirements for a patient with type 1 diabetes should mimic the insulin secretion of those without diabetes. If this is true, it means that the new equation should also estimate bolus insulin need for a patient with type 1 diabetes more accurately than before. This will be investigated in a future article.

A control system for the efficient operation of Bulk Air Coolers on a mine

The mining sector is a vital contributor to the economy of South Africa. This sector, however, consumes 15% of the countrys electrical energy. Deep mine operations require ventilation and cooling (VC) systems, which can account for up to 25% of the mines electricity cost. Refrigeration systems provide the cold water and air needed by the VC systems to mine at depths of over 2 km. Electricity cost savings on these refrigeration systems can be achieved by using time-dependent operating schedules. Peak-time electricity usage especially needs to be minimised to maximise these cost savings. The focus of this study was the development of a Bulk Air Cooler (BAC) controller, due to the lack of a controller to regulate these systems in the mining industry. This controller enables equipment to adapt dynamically to environmental changes by monitoring the underground temperature and adhering to input boundaries. The BAC controller was implemented on two sites, to control pumps, chillers and fans. A combined daily peak-time usage reduction of 4.3 MW was achieved on the two sites. This translates to an annual cost saving of R831 973. There is also a clear need to reduce electricity usage during the Eskom peak period. The BAC controller was therefore designed to monitor and control mine refrigeration machines. Equipment can thus be switched off during peak periods, provided the environmental parameters comply with safety regulations.

The design and development of a stented tissue mitral and aortic heart valve replacement for human implantation

Abstract A study was conducted into the development of a mitral and aortic heart valve replacement that caters for patients having suffered valve damage due to stenosis or rheumatic fever. The appeal of the valve is that it is constituted from a solid frame housing pericardial tissue leaflets, and allows the patient freedom from post-operative blood-thinning medication. The valve is designed to appeal to patients in developing areas of the world, as it features a clip-in mechanism to secure the valve assembly into the sewing ring, which is stitched in independently of the frame and leaflets. Re-operative valve replacement would then be made possible when the pericardial leaflets began to calcify. Novel aspects of the design added value to the science of heart valve replacements, through the use of sintered chrome cobalt in the valve components, the insights gained into mechanical testing of pericardium, and the patient benefits offered by the complete design. Further work is planned to fatigue test the assembly, undergo animal trials and make the valve available for commercial use.

A method for accurate electricity budget cost calculations for a deep mine

Electricity accounts for a significant portion of the total operating cost of many industries. It is therefore important for companies to accurately estimate future electricity cost. The increasing electricity tariffs greatly affect the consumers in South Africa. The annual active energy cost on an Eskom Megatlex tariff structure is 465% higher in 2015 than it was in 2007. It is therefore important for industries to measure and compare their daily electricity cost to an accurate electricity cost budget. Accurate cost budgeting is also a vital part of energy management. However, the electricity budgets that some consumers select are often over-simplified and can lead to misperceptions regarding system performance. A new method to calculate electricity budgets was therefore developed. This method uses additional parameters to calculate the electricity cost budgets. The most important parameter is time-of-use. The method is also expanded to calculate accurate cost budgets for sub-systems. A case study was conducted on a South African gold mine to analyse the performance and accuracy of the new method. The current method used by some consumers is also analysed and compared to this new method. For this case study the new method was 19 times more accurate than the method used by the consumer. This method uses a specific technique to calculate the electricity usage budget. Other techniques can be explored which might be more effective for different industries.

Preliminary Application of a New Bolus Insulin Model for Type 1 Diabetes

BACKGROUND Previous work derived a theoretically rigorous bolus insulin model. It was shown that the new model predicts insulin response of subjects without diabetes substantially better than the carbohydrate counting method (CHOcm). As most individuals with type 1 diabetes use the CHOcm, this article investigates if the new model can be applied to them. METHODS Equations are derived to characterize a person with type 1 diabetes. These are implemented on a cell phone that calculates bolus insulin dosages. In a small feasibility study the cell phone was used by 11 patients. Basal insulin remained unchanged. The subjects were experienced in the CHOcm and were using it at the start of the study. Continuous glucose monitoring data were recorded to capture blood glucose (BG) control elements such as average BG and tightness of control, as well as hypoglycemic and hyperglycemic events. A new rating method was proposed to estimate BG control. It (or a derivative thereof ) may in the future become a valuable measure of total glycemic control. We used the status quo ante versus status quo approach to find indicative results. BG control for the same group when using CHOcm (status quo ante) was compared with BG control when using the new application (status quo). RESULTS Patients found the new application on the cell phone practical. Indicative results also showed BG control improvements, although the subjects were more experienced in the CHOcm. Depending on the weights assigned to the underlying control elements an improvement of between 26% and 64% was found. CONCLUSION An indicative study (status quo ante vs. status quo) on 11 patients with type 1 diabetes showed that the new method can be practically and successfully applied on a cell phone. Glycemic control even improved. A new BG rating method was proposed. We believe there is enough preliminary indication to warrant a more detailed clinical trial in future by an institution with adequate funds and access to more patients.

Integration of electricity cost saving interventions on a water distribution utility

The efficient usage of electricity in the South African water industry has not been a priority due to the relatively low cost of electricity in the past. The situation has changed over the past years as a result of the rapid increase in electricity costs. South African water distribution utilities (WDUs) have installed capacities up to 450 MW. Not all WDUs operate efficiently. Therefore an intervention is needed to move towards efficient use of electricity in the South African water industry. Large combined installed capacity of the pumps and the large storage capacity make WDUs good candidates for load shifting projects. Due to the scale of the WDU and the complexity, the electricity cost saving approach needs to be integrated. Such an integrated approach could not be found in literature. An investigation methodology, as well as an integration strategy for the implementation of an electricity cost saving intervention is developed. The proposed integrated strategy is simulated and an optimised approach is developed. The proposed approach is implemented on a large water distribution utility in South Africa. The project realised an average electricity peak load shift of 15.4 MW. It is concluded that load shifting is possible on individual pumping stations in the water distribution utility subsystems.

Sustaining the performance of diverse energy management systems through reactive maintenance

Energy management systems (EMSs) form an important part of many Demand-Side Management (DSM) projects implemented on South African mines. Sustained EMS performance is only possible with proper system maintenance. However, it is challenging to maintain a large number of EMSs remotely. One of the main challenges associated with sustained EMS performance is changing production strategies. Although these changes require prompt revision of the EMS control strategy, energy services companies (ESCOs) typically use the daily EMS performance to assess the need for corrective maintenance. Thus, to improve the efficiency of EMS maintenance, a supervisory system was developed to facilitate reactive maintenance of different EMS technologies. This system prompts EMS maintenance based on diagnostics of key EMS components, the specific control strategy, and overall EMS performance. Results from two case studies using the system showed an increase in the EMS operational availability from 87% to 97%. The average EMS performance also increased from 1.7 MW to 2.6 MW. Seven additional implementations also improved average EMS operational availability from 72% to 95%, resulting in a combined performance of 19.2 MW compared to the 15.5 MW target. The abovementioned results prove that the developed supervisory system is able to facilitate sustained performance of a growing number of EMSs, by increasing the efficiency of the maintenance process.