Design And Development of a Solar Tracking System for the UPM Solar Collector

In solar energy system, sun tracking can significantly improve the efficiency of any solar array. Solar trackers periodically update the orientations of devices such as reflectors, solar panels or equipment to the actual position of the sun. From these points of view, we designed and developed a tracking system for the UPM solar collector. The system uses a software called Work-Bench in association with two data acquisition and control cards. The UPM solar collector uses two modes of tracking, passive and active tracks. The switch from active to passive is done automatically by comparing the irradiation to a preset value of 300 Wm-2. A manual tracking is also provided. This is required for initialization, shutdown, maintenance and emergency tasks. For the purpose of tracking, two independent stepper motor shafts are attached to the receiver. For the active tracking, the output voltages from two sun position sensors were used to activate the stepper motors. These two sun sensors convert the light intensity into voltage signals. Then by using the WorkBench software these signals are converted into logic signals to control the movement of the stepper motors. The passive tracking was carried out by utilizing the position angles of the sun. These angles were then resolved into two components for the east west and north south tracking. The WorkBench software was then used to convert these two components into voltages. The voltage was calibrated against a reference voltage produced by potentiometers attached to the motor shafts. The output from the comparison was used to control the movement of the stepper motors. Finally, the accuracy of the system was tested by taking the output resistance from a light dependent resistor attached to the receiver. The data indicated that the tracking is satisfactory since the output resistance from the light dependent resistor was approximately constant on a cloudless periods

Development of a Multi-Standard Protocol Using Software Defined Radio for a Mobile Station Transceiver

In this thesis, the Software Defined Radio Digital Control System (SDR DCS) has been developed to perform a multi-standard protocol of the handset using the GSM and CDMA systems. The SDR DCS was designed for the SDR based band digital transceiver of the handset as a control and protocol software to control and handle the operation of the handset when roaming between different protocols; it could easily and quickly let the handset reconfigure with the future protocol; it configured the handset with either of the GSM or CDMA protocol software, and scheduled for reconfiguration of the handset with the second protocol in sequence. The SDR DCS controls the download of the specific air interface environment. In order to implement the whole design in software, the design had to go through three stages. The first stage was to do all the design steps in the software using generic computing resources such as Hardware Description Language (HDL), with the top-level design for each protocol. The second stage was to define a logic circuit to perform the signal processing for each protocol; this step was applied after the simulation and synthesis, and eventually programming that circuit into the FPGA board. The third stage was to use the FPGA to implement the functions required for each protocol which constitutes the multi-standard protocol. The VHDL files were created for each element of the GSM and CDMA protocols. The GSM related system was developed with encoders and decoders linked to the channel model. The CDMA related system was designed with a transmitter to encode the user’s data into wide bandwidth using a reverse link channel and a synchronized receiver to receive the signal from the forward link channel and decode the wide bandwidth to recover the base band user’s data. The Synopsys™ software package was used for the design, synthesis and simulation of the SDR base band platform. The simulation tools used include the Model Sim and System Studio. Meanwhile, the Xilinx ISE 9.2i was used as the synthesis tool. The results of the simulated and synthesized top-level design files were downloaded into the Xilinx XSA-3S1000 FPGA board. The waveforms for the GSM and CDMA outputs approximately matched the ones seen in the oscilloscope for the FPGA output pin. This proved that the SDR DCS had successfully implemented its task, according to the objectives of the design

Incidence, Predictors, and Prognostic Impact of New-onset Atrial Fibrillation After Isolated Primary Coronary Artery Bypass Grafting

Background: New-onset atrial fibrillation (NOAF) after coronary artery bypass grafting (CABG) is associated with considerable morbidity and mortality. The objectives of this study were to estimate the incidence and predictors of NOAF after isolated primary CABG and evaluate its prognostic impact on the hospital outcomes of surgery. Methods: This study included 154 consecutive patients who underwent isolated primary CABG between October 2021 and February 2022. Patients were divided into two groups; Group 1 included patients with NOAF, and Group 2 had patients without NOAF. Results: NOAF occurred in 29 patients (18.8%). NOAF patients were significantly older (52.13± 6.30 vs. 55.45± 7.47 years; p =0.028), with more prevalence of diabetes mellitus but did not reach a significant level (62.1% vs. 44.8%; p = 0.094) and had a greater preoperative white blood cells count (WBCs) (8.87± 2.95 vs. 8.0± 2.17 /mm3; p = 0.071). Preoperative creatinine clearance (137.58± 53.94 vs. 114.94± 39.18 ml/min; p = 0.04), postoperative ischemic ECG changes (55.2% vs. 30%; p = 0.004), perioperative myocardial infarction (31% vs. 15.2%; p= 0.046), postoperative CK-MB (84.83± 81.26 vs. 64.76±46.58 units; p= 0.077), hemodynamic instability (72.4% vs. 41.6%; p= 0.003), and postoperative significant ECG changes (34.5% vs. 17.6%; p= 0.044) were greater in patients with NOAF. Age, preoperative creatinine clearance, preoperative WBC, and DM were associated with NOAF in the univariable analysis. None were found to be predictors of NOAF in the multivariable analysis. Conclusions: NOAF after isolated primary CABG is common. Advanced age, renal function, hemodynamic instability, and perioperative myocardial infarction might be associated with NOA

CO 2 Solubility in Hybrid Solvents Containing 1- Butyl-3-methylimidazolium tetrafluoroborate and Mixtures of Alkanolamines

International audienceTo reduce the rate of climate change, feasible and energy-efficient solutions need to be found to capture CO2 at low pressure from flue gas emitted by various industries and energy sectors worldwide. The use of solvents to selectively absorb CO2 is a promising option for CO2 capture. This research investigated the solubility of CO2 in hybrid solvents containing the 1-butyl-3-methyl imidazolium tetrafluoroborate [bmim][BF4] ionic liquid with mixtures of up to three alkanolamine solvents, namely monoethanolamine (MEA), diethanolamine (DEA), and methyl-diethanolamine (MDEA). Gravimetric analysis was used to measure equilibrium CO2 solubility in the hybrid solvents containing various compositions of the above components at CO2 partial pressures of 0.05 MPa to 1.5 MPa and temperatures of 303.15 K to 323.15 K. CO2 solubility in these solvents was benchmarked against pure ionic liquids, as well as conventional alkanolamine solvents, and modeled using the Posey−Tapperson−Rochelle model for the alkanolamines present and the SRK equation of state for the ionic liquid present in the hybrid solvents. It was found that the hybrid solventsachieved significantly higher CO2 solubility at low pressure than pure ionic liquids and conventional alkanolamine solvents. Modeling, however, was found to be less accurate for hybrid systems than data modeled for pure ionic liquid systems

Study and analysis of mobility, security, and caching issues in CCN

Existing architecture of Internet is IP-centric, having capability to cope with the needs of the Internet users. Due to the recent advancements and emerging technologies, a need to have ubiquitous connectivity has become the primary focus. Increasing demands for location-independent content raised the requirement of a new architecture and hence it became a research challenge. Content Centric Networking (CCN) paradigm emerges as an alternative to IP-centric model and is based on name-based forwarding and in-network data caching. It is likely to address certain challenges that have not been solved by IP-based protocols in wireless networks. Three important factors that require significant research related to CCN are mobility, security, and caching. While a number of studies have been conducted on CCN and its proposed technologies, none of the studies target all three significant research directions in a single article, to the best of our knowledge. This paper is an attempt to discuss the three factors together within context of each other. In this paper, we discuss and analyze basics of CCN principles with distributed properties of caching, mobility, and secure access control. Different comparisons are made to examine the strengths and weaknesses of each aforementioned aspect in detail. The final discussion aims to identify the open research challenges and some future trends for CCN deployment on a large scale

Factors associated with uncontrolled asthma among Sudanese adult patients

Objectives: Uncontrolled asthma is a major health problem resulting in increased morbidity, mortality, healthcare utilization, and costs. The aim of this study was to determine the level of asthma control and its associated factors in Sudan.Materials and Methods: We performed a cross-sectional study of 362 adult asthmatics consecutively recruited from the three main tertiary hospitals in Khartoum State-Sudan, between March and June 2018. Data were collected using standardized questionnaires and the asthma control test (ACT) was used to determine the level of control. Logistic regression analysis was used to determine factors associated with uncontrolled asthma.Results: The mean age of the subjects was 40.1 years (SD 15.7) and the sex distribution was almost equal, with 195 (53.9%) females. Among all asthmatics, the prevalence of uncontrolled asthma was 84.5%, according to ACT score. Factors associated with uncontrolled asthma included; health facility (odd ratios [OR] = 2.96 [1.27–6.86]), time to reach facility (OR = 4.51 [1.68–12.06]), non-adherence to follow-up visits (OR = 5.11 [1.12–23.36]), steroids tablets use without prescription (OR = 9.01 [1.01–79.88]), family history of asthma (OR = 0.45 [0.21–0.95]), and inhaler technique training (OR = 0.37 [0.17–0.78]).Conclusion: This study showed a high rate of uncontrolled asthma in three tertiary hospitals in Khartoum. Factors associated with uncontrolled asthma may be considered as targets for future intervention strategies

Moderate ischemic mitral regurgitation (IMR) and metabolic syndrome: where are we now and where are we going?

BACKGROUND: The metabolic syndrome appears to affect 10% to 25% of adult population worldwide. Several studies have described the association between metabolic syndrome and ischaemic heart disease, however, none linked metabolic syndrome to ischemic mitral regurgitation, a serious clinical problem facing both the cardiologists and cardiac surgeons. Ischemic mitral regurgitation is mitral insufficiency caused by myocardial infarction. The myocardial ischemia can result in altered ventricular geometry, leading to mitral insufficiency. Interestingly metabolic syndrome showed more pronounced alteration of left ventricular geometry and function especially in obese subjects. PRESENTATION OF THE HYPOTHESIS: We have recently proposed that there is link between metabolic syndrome and ischemic mitral regurgitation and associated complications. Operative strategy for moderate ischaemic mitral regurgitation continues to be debated between revascularisation alone and concomitant valve repair at the time of coronary artery bypass surgery. Each of the above group has published studies, with results supporting each argument. TESTING THE HYPOTHESIS: Generally speaking the treatments available for metabolic syndrome are based in both life style modification (dietary advice and advice to increase physical activity) and medical treatment to enhance insulin sensitivity. Randomised controlled trials may show whether the current available treatment of metabolic syndrome may have an impact on moderate ischemic mitral regurgitation. IMPLICATIONS OF THE HYPOTHESIS: Metabolic syndrome was shown to alter left ventricular geometry and therefore it is possible to postulate that the variation in the response of different patients with moderate ischemic mitral regurgitation to current management may be attributed to the absence and presence of metabolic syndrome. Research testing of this hypothesis in the future may reveal whether concomitant treatment of metabolic syndrome will play part in the management of moderate ischemic mitral regurgitation

Carbon dioxide capture methods for industrial sources.

Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2010.In order to reduce the rate of climate change, particularly global warming, it is imperative that industries reduce their carbon dioxide (CO2) emissions. A promising solution of CO2 emission reduction is Carbon dioxide Capture and Storage (CCS) by sequestration, which involves isolating and extracting CO2 from the flue gases of various industrial processes, and thereafter burying the CO2 underground. The capture of CO2 proved to be the most challenging aspect of CCS. Thus, the objective of this research was to identify the most promising solution to capture CO2 from industrial processes. The study focussed on capturing CO2 emitted by coal power plants, coal-to-liquids (CTL) and gas-to-liquids (GTL) industries, which are common CO2 emitters in South Africa. This thesis consists firstly of an extensive literature review detailing the above mentioned processes, the modes of CO2 capture, and the various CO2 capture methods that are currently being investigated around the world, together with their benefits and drawbacks in terms of energy penalty, CO2 loading, absorption rate, capture efficiency, investment costs, and operating costs. Modelling, simulation, and pilot plant efforts are also described. The study reviewed many CO2 capture techniques including solvent absorption, sorbent capture, membrane usage, hydrate formation, and newly emerging capture techniques such as enzyme based systems, ionic liquids, low temperature cryogenics, CO2 anti-sublimation, artificial photosynthesis, integrated gasification steam cycle (IGSC), and chemical looping combustion The technique of solvent absorption was found to be the most promising for South African industries. Vapour-liquid-equilibrium (VLE) measurements of solvent absorption using amine blends were undertaken, using blends of methyl-diethanol amine (MDEA), diethanol amine (DEA) and water (H2O) with composition ratios of 25: 25: 50 wt% and 30: 20: 50 wt% respectively, and with CO2 and N2 gases at CO2 partial pressures of 0.5 to 10.5 bar. Experiments were conducted under system pressures of 5 to 15 bar and temperatures of 363.15 and 413.15 K, using a static analytic apparatus. CO2 liquid loading results were analysed and discussed. The experimental data were regressed in Matlab (R2009b) using the Posey-Tapperson-Rochelle model and the Deshmukh-Mather model. The Matlab programmes are presented along with the regressed binary interaction and model parameters. The accuracy of model predictions are discussed. Thereafter an Electrolyte-NRTL model regression and simulation of the absorption process was conducted using Aspen Plus V 7.1. for flue gas compositions, solvent compositions, temperature, and pressure conditions similar to that of process operating conditions. CO2 loading, design factors, CO2 recovery, and CO2 purity results were analysed and compared where appropriate, with experimental results. Finally a general preliminary energy efficiency and cost analysis was conducted based on the simulation results. The main conclusions reached are that the amine solvent blend containing 25:25:50 wt% of MDEA:DEA:H2O, produced higher CO2 loadings for its respective system conditions than other solvents studied and those found in literature. However, absorption of CO2 was found to be highly dependent on system temperature and pressure. The Deshmukh-Mather model provided higher accuracy than the Posey-Tapperson-Rochelle model, producing CO2 loading predictions with a relative error not exceeding 0.04%, in 1.5 to 3 minutes using a dual core processor. Aspen absorption simulations provided significantly lower CO2 loading results than those experimentally obtained, due to the low contact time achieved and higher temperature dependence in the proposed absorption process. Process improvements were highlighted and implemented to increase CO2 recovery and purity. Energy penalty values were found to be higher than those found in literature, but room for process and design improvement was identified and recommendations were given. Investment cost estimates were found to be justifiable and within reason. Limitations of the simulation were also identified and discussed

Engineering students and their prospective employers: expectations and reality.

Masters Degree. University of KwaZulu-Natal, Durban.Since the dawn of democracy in South Africa in 1994, numerous changes have occurred at tertiary institutions to enable greater access for people of all backgrounds and increased graduate throughput to fulfil the needs of the labour market for engineers. Widespread changes in the size and composition of successive undergraduate engineering cohorts have occurred. Simultaneously, the needs of industry have undergone significant changes due to the information age, globalisation and the rapid increase in technological advances and access to technology. This study attempted to assess the alignment between the expectations of students who have graduated in engineering, the expectations of engineering employers and reality. A mixed methodology was developed. The study firstly surveyed engineering graduates at the University of KwaZulu-Natal (UKZN) using a questionnaire developed for quantitative analysis. Convenience sampling and a positivist approach were used. Graduates’ needs, study approaches, employment and workplace expectations were determined, analysed and interpreted through the lens of three frameworks, namely Biggs’ study motives and strategies, Bloom’s taxonomy and Boundaryless and Protean careers. Secondly, the study surveyed all engineering discipline academic leaders at UKZN by qualitative, semi-structured interview within an interpretivist paradigm and using deductive thematic semantic analysis. Academic leaders were used as a proxy for obtaining industry opinion and expectations and questioned on a number of themes including graduate and employer expectations, positive or negative trends, graduate training programmes, further training and postgraduate study, exit-level outcomes (ELOs) and graduate attributes, the reality of mis-alignment and what UKZN can do to limit it. Responses were collated and compared quantitatively and qualitatively where appropriate. A number of issues and mis-alignments was identified together with causes of mis-alignment. Mis-alignment was identified in salary, growth and guidance expectations, confidence, software and niche proficiencies and innovation expectations. Key causes included language barriers, lack of engineering hobbyist backgrounds, workload and study strategies, assessment changes and personal responsibility. Findings were discussed within the three theoretical frameworks mentioned above and summarised in light of the objectives of this study. Recommendations for UKZN to play a role in mitigating many of the issues and misalignment were provided, along with recommendations for any possible future research in this area