Mathematical modelling, flight control system design and air flow control investigation for low speed UAVs

The demand for unmanned aerial vehicles (UAVs) has increased dramatically in the last decade from reconnaissance missions to attack roles. As their missions become more complex, advances in endurance and manoeuvrability become crucial. Due to the advances in material fabrication, wing morphing can be seen as an ideal solution for UAVs to provide improvements by overcoming the weight drawback. This thesis investigates the area of aircraft design and simulation for low speed UAVs looking at performance enhancements techniques for low speed UAVs, and their effects on the aerodynamic capabilities of the wing. The focus is on both suitable control design and wing morphing techniques based on current research findings. The low speed UAV X-RAE1 is used as the test bed for this investigation and is initially analytically presented as three dimensional body where the equations relate to the forces and moments acting on the UAV. A linearised model for straight flight at different velocities is implemented and validated against a non-linear model. Simulations showed the X-RAE1 to have acceptable stability properties over the design operating range. Control design techniques, linear quadratic regulators (LQR) and H-infinity optimisation with Loop Shaping Design Procedure (LSDP), are used to design simple control schemes for linearised longitudinal model of the X-RAE1 UAV at different velocities. The effectiveness and limitations of the two design methods show that both designs are very fast, with settling times 2-3 seconds in the height response and remarkably low variation of the results at different velocities. Computational fluid dynamics is then used to investigate and simulate the impact of introducing smart effector arrays on a UAV. The smart effector array produces a form of active flow control by providing localised flow field changes. These induced changes have direct impact on the aerodynamic forces and showed a substantial increase of lift at low angles of attack. There was also a significant increase to the lift to drag ratio at high angles of attack which resulted to a delay in stall

Induced Voltages on a Gas Pipeline due to Lightning Strikes on Nearby Overhead Transmission Line

The purpose of this paper is to investigate the severity of lightning induced voltages on a gas pipeline installed in parallel with overhead transmission line using two different simulation packages. The results from this study using CDEGS, which solves a given problem based on electromagnetic computations, reveal that the induced voltages on the pipeline are more accurate compared to that obtained by PSCAD simulation, which is based on the circuit approach. Unlike PSCAD, CDEGS considers many salient factors such as soil model, inductive, capacitive and conductive couplings, and multiple soil structures.  Models of a double circuit 132kV transmission line, gas pipelines, soil with different resistivities and variable lightning surges were developed. The effects of pipelines located at various heights above ground and distance of pipeline from the power lines were also studied. Compared to previously published work using PSCAD, it is found that CDEGS has given more accurate results. Several findings which were not possible using PSCAD were observed such as the effect of soil structure on induced voltage and multiple layers soil. This also led to better understanding of the conductive coupling from lightning strikes and fault conditions. The modeling work using CDEGS not only useful for providing more reliable data for further protection and mitigation techniques, but is  also very versatile to study the effects of various other important factors affecting the induced voltage on the pipelines.

The impact of digitalization on credit risk: the mediating role of financial inclusion (National Bank of Egypt (NBE) case study)

This article investigates potential direct and indirect impact of National Bank of Egypt (NBE) digitalization and its financial inclusion on credit risk. The methodology used in the study is an empirical technique through the collection of secondary data from the period between 2011 and 2021 in the Egyptian banking sector. To accomplish this, the study developed two hypotheses employing the empirical SEM model for testing whether there is a positive or negative impact for three chosen variables: digitalization, credit risk and financial inclusion. The investigational outcome shows that NBE digitalization has both direct and indirect impact through the mediator variable, financial inclusion. It also provides an understanding of the relationship between digitalization, credit and financial inclusion. The article proposes for future studies the impact of other Fintech factors directly and indirectly using the mediators on credit risk. The authors came up with many findings: first, financial inclusion indices can be built using portable money and banking services activities. Second, digitalization has a negative direct impact on credit risk. Also, digitalization has a positive indirect impact on credit risk through the mediator variable which is referred to as financial inclusion. Third, the model fit is adequate for the data being tested

Evaluation of the role of ischemia modified albumin as a new biochemical marker for differentiation between ischemic and hemorrhagic stroke

Objective: To evaluate the role of the detection of ischemia modified albumin (IMA) level in the differentiation between ischemic and hemorrhagic cerebrovascular stroke.Methods: Sixty elderly persons classified into three groups, 25 patients diagnosed with cerebral infarction, 15 patients diagnosed with cerebral hemorrhage, and 20 elderly healthy persons with matched age as control  were enrolled in the study. IMA was measured using the available chemical method and computerized  tomography (CT) was done for diagnosis of brain lesions.Results: IMA was significantly higher in the patient group than in the control group. There was a positive significant correlation between age, albumin with IMA, (P =0.000 and 0.037 respectively). However there was no statistical significant difference between sex and diagnosis cross tabulation (0.51). It was found that, IMA was statistically higher in the infarction group than the hemorrhage group (P = 0.000) and IMD index was statistically higher in the infarction group than the hemorrhage group (P = 0.013).Conclusion: Our investigation in elderly patients suggests that IMA assay is a sensitive marker forearly detection of ischemic and hemorrhagic stroke

Tropospheric Scintillation with Rain Attenuation of Ku Band at Tropical Region

Tropospheric scintillation can become a significant impairment in satellite communication systems, especially in tropical regions with frequencies higher than 10 GHz, the attenuation is dramatically affecting the scintillation. This work concentrates on those aspects in equatorial Johor Bahru, Malaysia, based on a one-year Ku-band propagation measurement campaign, utilizing the equipment of Direct Broadcast Receiver (DBR) and Automatic Weather Station (AWS). This study investigates the relationship between wet scintillation and rain attenuation using experimental measurement and concentrate on the probability density function (PDF) of different scintillation parameters. From the results, it is concluded that wet scintillation intensity increases with rain attenuation. Thus, the relationship can be phrased by linear equations or power-law. The PDFs of wet scintillation intensity, adapted to a given rain attenuation level, are found lognormally distributed, leading to selection of method for determining the relation between conditional PDFs and rain attenuation

Evaluation of serum hepcidin in assessment of iron status in renal transplant patients

Background: Hepcidin is a 25 aminoacid peptide that isproduced primarily by the liver in response to a varietyof stimuli known to modulate tissue iron stores and itsserum availability. It circulates in plasma, is filtered bythe kidney, and accumulates in urine. The presence ofhepcidin in the plasma negatively regulates the egress ofiron from the cells and macrophages, involved intransport of iron into the extracellular spaces. Hepcidinbinds to ferroportin 1 present on the cell surface leadingto the internalization of ferroportin 1 and subsequentdegradation. Hepcidin has also been shown to be anacute phase reactant increased by interleukin 6 (IL-6) andmarkedly induced by infection and inflammation.Documentation of the role of hepcidin in thedevelopment of anemia in chronic kidney disease andwhether it can be used as a marker of iron status inchronic kidney disease (CKD) has been sought in manystudies.The aim of this study was to detect the value of hepcidinas a marker of iron status in post renal transplantrecipients as compared with chronic renal failure (CRF)patients on hemodialysis.Results: In our study we found the level of serumprohepcidin in the renal transplant recipient group to becomparable to the control group. In the group with CKDthe serum prohepcidin was significantly lower thancontrols as well as the transplant recipients (p-value:0.00). There was no significant difference between theCKD group with higher hemoglobin and those withlower hemoglobin. From the correlation between theacute phase proteins and prohepcidin we found a positivecorrelation between serum ferritin, CRP and prohepcidinonly in the group with CKD on hemodialysis.Conclusion: We suggest that serum prohepcidin can be used as a routine measurement in transplant recipients as an indicator of the iron stores in the body. Further dedicated studies on large groups of patients need to be done to verify the usefulness of such a test

Power transmission lines electromagnetic pollution with consideration of soil resistivity

The alternating current (AC) total interference of power lines may pose a threat to personnel and equipment in its vicinity. The main objective of this work is to determine the electromagnetic distribution and induced voltages on human body, equipment, and houses due to the AC total interference for different soil resistivities. The electromagnetic field and induced voltages may cause health problems to the human body and put it at risk. Two main approaches were used to compute the electromagnetic and induced voltages, namely the field approach, which is based on electromagnetic field distribution, and the circuit approach, which uses the circuit grounding analysis to compute the conductive interference and then uses the circuit based models to compute the inductive interference. Human body, steel houses and 10-km-long transmission line were modelled. The soil resistivity was varied, and the induced voltages obtained from both approaches were compared. Soil resistivity and soil structure are important parameters that affect the AC interference level. The results show that the touch voltage increases when the distance between electromagnetic source and human body increases. For high soil resistivity, the danger of the touch voltage becomes more prominent compared to that for low soil resistivity. Power system voltage level and soil resistivity are two key factors influencing the induced voltage level

Comparison of lightning return stroke channel-base current models with measured lightning current

Electromagnetic pulse radiation produced around the lightning stroke channel has caused the disturbance to the microelectronic industry, especially to disturbance of high frequency to electronic systems. Lightning channel-base current function (CBC) characteristics and parameters determine lightning electromagnetic field (LEMF) results obtained on the basis of the used models. This paper evaluated and compared the measured lightning current and six lightning current-based channels models namely Bruce and Golde, Heidler, Diendorfer and Uman, Nucci, Pierce and Cianos and new current-based current (NCBC) models. In terms of the waveshape, among all the six lightning channel-based current models discussed, the models developed by Javor, Nucci and Diendorfer and Uman have showed a good agreement compared to the measured lightning current. In terms of 10-90% risetime and full width half maximum time (FWHM) comparison, NCBC and Nucci models have showed compatible comparison. However, Nucci model is not easily adjustable to different desired pulse-current waveshapes. On the other hand, NCBC model can be simplified, the values of lightning peak current and risetime can be chosen arbitrarily and independently from other parameters, and there is no need for the peak-correction factor, so that reduces the number of parameters. Therefore, the NCBC model was suggested to be used in the future in order to simulate much accurate return stroke model. This knowledge will contribute to the development of a new accurate and efficient return stroke model

Characterization of concurrent Ku band tropospheric scintillation and rain attenuation in Malaysia

Tropospheric scintillation in satellite communication systems operating at frequencies over 10 GHz is a significant impairment, especially in tropical regions, as attenuation affects scintillation dramatically. This work concentrates on tropospheric scintillation in equatorial Johor Bahru, Malaysia, based on a one-year Ku-band propagation measurement study utilising a direct broadcast receiver and an automatic weather station. This study aimed to investigate the relationship between wet scintillation and rain attenuation using experimental measurements. The power spectral analysis has been carried out to determine required cut-off frequency of filtering to separate out rain attenuation and scintillation effects. The results can provide significant information on the fluctuations of wet scintillation at Ku-band earth space link in tropical regions