Model predictive control for current balancing in a four-phase buck converter

Multiphase buck topology offers smaller ripple current and lower component ratings. This, however, compromises unbalanced output current between each phase of an inductor which leads to over-current and inductor saturation issues. Often when discussing the linear control schemes, it involves the use of superposition theorem to understand the system’s response. However, the limitation of superposition theorem in this application is that it assumes the circuit to be completely linear. For components with nonlinear behaviour such as power switches and diodes, the analytical results may not be accurate resulting to unexpected behaviour as the algorithm is implemented on a real system. Hence, the use of a more advanced control scheme is necessary to improve a system with a non-linear characteristic. This paper proposes a current limit control (CLC) consists of MPC for inner loop control and PID for outer loop control for phase current balancing in a four-phase buck converter. The controller is designed to achieve balanced current for each phase with acceptable response time. The proposed system is designed using MATLAB/Simulink simulation software and verified by a laboratory prototype with a TMS320F28335 as the main controller. Simulation and experimental results are provided to validate the system performance

Improvement of speed response in four-phase DC–DC converter switching using two shunt voltage-source

This study proposes a technique that is able to improve the speed response of a four-phase DC–DC converter switching. The basic concept of the proposed technique is the inclusion of two shunt-connected voltage sources in series to the converter system. Using a higher input voltage to drive the load, a higher current per microsecond output system will be obtained and reverts to its nominal input upon obtaining desired references. Thus, the transient response observed when using this proposed technique is found to be much faster when compared to the conventional converter. Moreover, this technique is easily implemented as it requires only an additional voltage source, power switch, and power diode. The integrated model of the two shunt voltage-source in a four-phase DC–DC converter was simulated in MATLAB/Simulink and validated against the experimental results of a laboratory prototype, 600 W four-phase DC–DC converter. The novelty of this proposed technique is its ability to provide faster operations for critical loads applications, lower output capacitor and lower operating frequency

Indigenous knowledge in the management of a community-Based Forest Reserve in the Wa West District of Ghana

Despite the various awareness-creation exercises on community-based management systems by the Forestry Commission and Environmental Protection Agency of Ghana, there appear to be no appreciation of the role of indigenous knowledge in the process. Specifically in the case of the management of the forest reserves, no effective formal strategies exist as yet for working with rural communities to accomplish the goals of nature conservation using local experiences and knowledges. Yet, for the many communities involved in the management of forests and other nature reserves, their local knowledges and experiences have been instrumental in the management of their environments and their resources. This paper evaluates the contributions of indigenous knowledge in community-based management of the natural vegetation by focussing on the case of the Yuoboli Integrated Forest Reserve of the Naaha community in the Wa West District of Ghana. It examines the role of indigenous knowledge in the lives of the people of Naaha and the effectiveness of the strategies used for the management of their natural vegetation. Qualitative and quantitative approaches were used to collect data from primary and secondary sources. The study reveals that conventional approaches are complemented with indigenous knowledge in the management of the Yuoboli Forest Reserve. Also, cherished indigenous methods of managing the reserve are sacrifices, creation of fire belts and taboos such as ‘‘no hunting’’, ‘‘no burning’’ and ‘‘no cutting of trees.’’ The study indicates that 81.3% of the interviewees supports the making of fire belts as one of their respected indigenous ways of managing the reserve and in that respect, 98.4% affirm that indigenous knowledge supports development. It is recommended that their indigenous knowledge on natural resources management be deepened by the creation of institutions within the community to support the process in order to ensure easy learning and knowledge transfer to subsequent generations. Also, organisations should give support to the community on how to effectively manage the reserve locally. This will encourage participation and empowerment.KEY DESCRIPTORS: Indigenous knowledge, Natural Resources Management, Environmental Degradation, Community-based Approaches, Forest Reserves

The Effects of Banana Peels on Blood Parameters of Grower Rabbits

The study was conducted to assess the blood parameters of grower rabbits fed inclusion levels of banana peels meal (BPL). A total of thirty six (36) grower rabbits aged 5-7 weeks with mean initial weight of 837.50+ 0.2g were used. The parameters taken were initial weight and blood samples for analysis. Significant differences were observed in all the parameters measured (p<0.05) except initial weight, red blood cells and white blood cells (p>0.05). The mean weekly weight gain of the rabbits on diet T4 was highest but relatively similar to that of T2 and T3 (p>0.05). Based on the results obtained, banana peels has no detrimental effects on rabbits hence should be fed up to 30% inclusion level, and at the same time reduce the competition between man and animal for conventional ingredients such as maize, rice, guinea-corn and their offal's etc. Keywords: Banana peels meal, growing rabbit, Blood Parameter

Experimental implementation controlled SPWM inverter based harmony search algorithm

An optimum PI controller using harmony search optimization algorithm (HS) is utilized in this research for the single-phase bipolar SPWM inverter. The aim of this algorithm is to avoid the conventional trial and error procedure which is usually applied in finding the PI coefficients in order to obtain the desired performance. Then, the control algorithm of the inverter prototype is experimentally implemented using the eZdsp F28355 board along with the bipolar sinusoidal pulse width modulation (SPWM) to control the output voltage drop under different load conditions. The proposed overall inverter design and the control algorithm are modelled using MATLAB environment (Simulink/m-file Code). The mean absolute error (MAE) formula is used as an objective function with the HS algorithm in finding the adaptive values of  and  parameters to minimize the error of the inverter output voltage. Based on the output results, the proposed voltage controller using HS algorithm based PI (HS-PI) showed that the inverter output performance is improved in terms of voltage amplitude, robustness, and convergence rate speed as compared to PSO algorithm based PI (PSO-PI). This is to say that the proposed controller provides a good dynamic responses in both cases; transient and steady-state. Finally, the experimental setup result of the inverter controller is verified to validate the simulation results

The preparation and characterization of chitosan/poly (vinyl alcohol) blended films : mechanical, thermal and surface investigations

In this study, blends of chitosan (CS) and polyvinyl alcohol (PVA) (CS/PVA) having various proportions were prepared and characterized by universal mechanical tester, the differential scanning calorimetry (DSC) and contact angle measurements. Studying the mechanical properties of the films showed that blending improved the tensile strength, which increased with increasing PVA content up to 40% while the elongation% at break of the blends was decreased compared to that of the pure components. The obtained results of DSC suggested that some interaction between chitosan and PVA mostly took place. Static water contact angle measurements showed an improvement in the wettability of the obtained films

Individual and community-level socioeconomic position and its association with adolescents experience of childhood sexual abuse : a multilevel analysis of six countries in Sub-Saharan Africa

Background: Childhood sexual abuse (CSA) is a substantial global health and human rights problem and consequently a growing concern in sub-Saharan Africa. We examined the association between individual and community-level socioeconomic status (SES) and the likelihood of reporting CSA. Methods: We applied multiple multilevel logistic regression analysis on Demographic and Health Survey data for 6,351female adolescents between the ages of 15 and 18 years from six countries in sub-Saharan Africa, between 2006 and 2008. Results: About 70% of the reported cases of CSA were between 14 and 17 years. Zambia had the highest proportion of reported cases of CSA (5.8%). At the individual and community level, we found that there was no association between CSA and socioeconomic position. This study provides evidence that the likelihood of reporting CSA cut across all individual SES as well as all community socioeconomic strata. Conclusions: We found no evidence of socioeconomic differentials in adolescents’ experience of CSA, suggesting that adolescents from the six countries studied experienced CSA regardless of their individual- and community-level socioeconomic position. However, we found some evidence of geographical clustering, adolescents in the same community are subject to common contextual influences. Further studies are needed to explore possible effects of countries’ political, social, economic, legal, and cultural impact on Childhood sexual abuse

Reliability and Inequality Measures for the Weimal Distribution

Reliability analysis basically deals with the probability of survival or failure (death). This article aimed at discussing both reliability and inequality measures from the Weimal distribution. The work has derived and discussed theoretically, expressions for the survival and hazard function of the Weimal distribution. The ordinary and incomplete moments of the distribution were also obtained. Lastly, some inequality measures for the distribution were derived using the moments of the distribution.Keywords: Reliability; Inequality measures; Moments; survival function, hazard function, income distribution

Corrosion study of pipeline material for seabed sediment in tropical climate

Corrosive environments such as marine sediments can cause corrosion to steel pipelines at any time when certain conditions are met. Seabed sediment could cause severe corrosion damage due to its corrosiveness to the pipelines buried under it. Many consequences could take place in case if there is incident in oil/gas pipelines. Successfully identifying elements of corrosion in marine sediment would enhance the future of steel structure protection and monitoring systems. This article focuses on the behaviour of corrosion rate of steel located near shore environment and the aim is to determine the effect of sediment on corrosion of steel. To investigate that, simulated near shore sediment conditions have been used where the steel coupons buried in sediments which have different characteristics. Weight loss technique has been implemented to determine the weight loss rate of the steel specimens. Based on the results of this study, metal weight loss increases as the duration of exposure to seabed sediment environment become longer. The sea sediment simulated condition has given significant levels of corrosion. Conclusively, the corrosion rate of steel in seabed sediment located in tropical region is complicated and further studies are suggested