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Through this research, polymeric composites were prepared from epoxy as a base material with isobutyl rubber (waste rubber washers powder for water taps) and this was done by adding different weight percentages of isobutyl rubber. This was done by adding different weight percentages of isobutyl rubber. After a series of experiments, it was found that the best weight percentage was (5%).This addition was done at different temperatures (8,25,55) °C. The results when compared before and after the reinforcement process for the composites showed that the thermal conductivity decreased after the reinforcement process, as for the resistance to hardness and compressibility, it increased after reinforcement, but it was less valuable for the hardness and compressibility at the temperature (55) °C compared to the results at (8) °C. As for the shock resistance, its value increased after reinforcement, and the increase was greater at the temperature (55) °C compared to its value at (8) °C.

A Stable and highly reliable DC link voltage represents an important factor for efficient power transfer in high voltage direct current (HVDC) networks. In this framework, this paper investigates the control and stability analysis of voltage source converter (VSC) for DC link voltage regulation. To separately achieve the independent active and reactive power control, the system voltages and currents are represented in the synchronous reference frame. In order to optimally design the parameters of proportional-integral (PI) controller, the inner and outer loops’ transfer functions are thoroughly derived/developed. In addition,/moreover, in order to attain satisfactory/certain system performance, modulus optimum, symmetrical optimum pole placement control approaches are studied and implemented for the purpose of tuning the voltage/current controller gain parameters. In particular for the symmetrical optimum control method, the gain parameters of the DC-bus voltage are determined under different values of network impedance. Furthermore, the impact/influence of changing gain parameters on the DC-link voltage and poles/zeros movement are investigated. MATLAB/Simulink model is built and simulation studies are carried out to verify the introduced concepts.

Background Rational drug management has become an increasingly important topic in order to make optimal use of the drug budget to offer health services of the highest possible standard. It is important that continuous assessment for rational prescribing and use of drug have to be carried. Objective of this study was to gather data on existing drug prescription and dispensing practices and to evaluate the prescribing and dispensing indicators as described by the WHO. Method Observational, cross-sectional, prospective study was designed and conducted to evaluate the performance of hospital and community pharmacies in Khartoum state, related to rational drug use and prescribing and dispensing practices during the period from November 2018 to March 2019. 297 Hospital and community pharmacies from public and private sectors were contacted for carrying out this study survey and the collected data were analysed against WHO standards for core drug use indicators. Results The average number of drugs per encounter was 3.98 drugs. Hospital pharmacies had a higher (4.18±1.516) number of drugs prescribed than community pharmacies (3.87±1.331) with significance difference between mean of two types of pharmacies (P = 0.015). The percentage of antibiotic per prescription was (53.7%). Antibiotic prescribing was much higher (54.0%) in the hospital pharmacies compared to (48.6 %) in community pharmacies. The average percentage of injections per prescription at the facilities was found to be (57.6%). The percentage of prescription with written diagnosis was (26%.0) and the percentage of prescriptions with written dose was (78%.0). The average dispensing time was (1.75) minutes, The Percentage of drugs actually dispensed was (55.99%), the average adequacy of labelling of drugs was (30.4%). Overall prescribing and dispensing indicators were higher than WHO standard. Conclusion The degree of poly pharmacy was greater than of WHO criteria. The completeness and rationality of prescription was found suboptimal and components were missed.