Numerical investigation of atmospheric icing on wind turbine blades

The research work presented in this thesis aims to predict ice accretion effect on a wind turbine blade section at 80% of blade span. All simulations are obtained using FENSAP ICE, a widely used solver for aircraft in-flight icing simulations. Using low and high liquid water concentrations existed in clouds at lower altitudes, different icing events are simulated. Ice accretion predictions are computed using single-shot and multi-shot approaches. Blade surface roughness is investigated, as well as the relationships between ice mass, liquid water content, median volume diameter and temperature are predicted. To study the effect of blade design / curvature parameters on the ice formation process, ice accretion loads are predicted for all NREL airfoil families used for horizontal axis wind turbines. The effect of low and high LWC conditions on blade thickness is presented. Effects of atmospheric temperature, LWC, MVD and flow angle of attack on resulted ice shape are investigated. The degradation in aerodynamic characteristics due to ice formation is investigated at different icing conditions. The new numerical data presented in this thesis provide useful insights on ice accretion rates for wind turbines operating in cold and harsh environments

Scaling of multiphase flow, droplet trajectories, and ice accretion on a rotating wind turbine blade

This thesis presents an extended formulation of non-dimensionalized governing equations for scaling of the flow field, droplet trajectories, and ice accretion on a rotating wind turbine blade. The analytical formulation leads to similitude relationships for ice accretion to evaluate new scaling parameters corresponding to the rotation of the blade. The scaling methodology can be used to determine alternative test conditions and predict icing conditions on a full-scale wind turbine blade. The main objective of the research is to develop and apply scaling methods and similitude analyses for ice accretion prediction on a rotating turbine blade. The investigation reviews the derivation of the similitude relationships for ice accretion scaling to evaluate their importance and develops new scaling parameters corresponding to the rotation of the turbine blade. Numerical CFD icing simulations are also performed using ANSYS FENSAP ICE software to test the proposed scaling methods and verify the results. A turbine blade model is developed using blade element momentum theory (BEM). Turbine blade models are scaled up in geometry, and each case is tested at specific flow conditions as calculated using the scaling equations. Scaled conditions for velocity (streamwise and rotational), droplet size, and icing time are examined. CFD solutions for the flow field (air and droplet) are obtained in terms of velocity, droplet trajectories, pressure coefficient distributions, ice thickness, and ice shapes by quantifying the significant parameters involved in the icing process. Recommendations for parameters to be used for glaze and rime ice scaling on a rotating blade are presented and new numerical predictions are provided to support those recommendations. Numerical results and test conditions are obtained at sea level in wind tunnel facilities for experimental investigation. The research results provide valuable insight to predict ice accretion on large wind turbine blades in the field, based on smaller scaled blade models tested in a laboratory setting

Two spectrophotometric methods for the determination of azithromycin and roxithromycin in pharmaceutical preparations

Two new and simple spectrophotometric procedures have been proposed and validated for estimation of two important macrolide antibiotics namely, azithromycin dihydrate and roxithromycin. Method I depends on complex formation between any of the two drugs and copper in acidic medium where the absorbances of the produced complexes are measured at 250 and 264 nm with linearity ranges of 1.0-100.0 and 2.0-130.0 µg/mL for the two drugs, respectively. Method II depends on the reaction of these drugs with N-bromosuccinimide forming a product which is yellow colored, measured at 264 and 278 nm, with linearity ranges of 2.0-140.0 and 3.0-160.0 µg/mL for azithromycin dihydrate and roxithromycin, respectively. The proposed methods were subjected to detailed validation procedure; moreover they were used for the estimation of the concerned drugs in their different dosage forms. Study of the reactions stoichiometry was carried out; furthermore, a reaction mechanism proposal was presented

Machine learning models for traffic classification in electromagnetic nano-networks

The number of nano-sensors connected to wireless electromagnetic nano-network generates different traffic volumes that have increased dramatically, enabling various applications of the Internet of nano-things. Nano-network traffic classification is more challenging nowadays to analyze different types of flows and study the overall performance of a nano-network that connects to the Internet through micro/nanogateways. There are traditional techniques to classify traffic, such as port-based technique and load-based technique, however the most promising technique used recently is machine learning. As machine learning models have a great impact on traffic classification and network performance evaluation in general, it is difficult to declare which is the best or the most suitable model to address the analysis of large volumes of traffic collected in operational nano-networks. In this paper, we study the classification problem of nano-network traffic captured by micro/nano-gateway, and then five supervised machine learning algorithms are used to analyze and classify the nano-network traffic from traditional traffic. Experimental analysis of the proposed models is evaluated and compared to show the most adequate classifier for nano-network traffic that gives very good accuracy and performance score to other classifiers.This work was supported in part by the ‘‘Agencia Estatal de Investigación’’ of ‘‘Ministerio de Ciencia e Innovación’’ of Spain under Project PID2019-108713RB-C51/MCIN/AEI/10.13039/501100011033, and in part by the ‘‘Agència de Gestió d’Ajuts Universitaris i de Recerca’’ (AGAUR) of the ‘‘Generalitat de Catalunya’’ under Grant 2021FI_B2 00091.Postprint (published version

Ecological studies on the ciliate and bacterial populations of slow sand filters

This study deals with the ecology of ciliate and bacterial populations in operational slow sand filter beds used as a stage in treatment of river water for drinking water supply. It differs from earlier research in this college on the meiofauna and protozoa of similar filter beds in the source of water, the use of micro-strainers for pre-treatment, the coarser composition of the sand and in the study of bacteria. Three beds were studied but only one of these was studied for 9 runs, starting immediately after resanding in March 1985 and finishing in December 1985. The other beds were investigated comparatively to assess the effects of excluding sunlight. The sampling programme was designed to provide a time-course of depth distribution of densities of the ciliate protozoan and bacterial populations as well as the abundance of particulate organic carbon and chlorophyll a in relation to measures of the bed's performance such as head loss and filtration rates, which were monitored by Thames Water.Fourteen species of Ciliatea were commonly recorded and were counted alive after extraction from the sand at different depths and cold sedimentation. The same depths were used to determine the concentration of particulate organic carbon and chlorophyll a as well as the density of bacteria shaken off the sand grains and counted by incidence epifluorescence microscopy. As only single cores were taken on each sampling occasion due to the need to sample frequently, at many depths and to count live organisms, a special study was undertaken to estimate the horizontal variability of protozoan and bacterial densities. Tests were made on the extraction efficiency ofthe protozoan and bacterial techniques. Scanning electron microscopyof the sand grain surfaces from different depths was used to determine the sizes and shapes of the bacterial forms present as well as to assess the efficiency of the shaking technique for their removal. Thelinear dimensions of the different ciliate species were also measured. This permitted the calculation of cell volume of each common species, using formulae for the most appropriate geometric shape.Three phases of development in ciliate depth distributions occurred in most runs: during the first four days, ciliate densitieswere low and uniform throughout the depths; this was followed by increased densities in the top few cms and a sharp decline with depth; after the third week of the run, a marked surface avoidance was observed. The bacterial populations and the concentrations of POC and chlorophyll a showed similar patterns of depth distribution with time, with the exception of the phase with surface avoidance.The bed exposed to normal levels of sunlight was more productive than the other covered beds which was shown by the bacteria, ciliates, chlorophyll a and POC. Peak ciliate densities occurred during the third week of a run in all three beds but the highest bacterial densities appeared earlier (13-14 days) in the unshaded bed compared with the shaded ones (31 days). In all three beds, a marked decline in ciliate densities coincided with an increased development of the bacterial populations. During the first ten days of a run when head loss increased slowly, the ciliate and bacterial populations were able to increase their densities exponentially accompanied by an increasing cumulation of POC and chlorophyll a. This was followed by a period when the head loss increased more markedly when the ciliates, bacteria and chlorophyll a concentrations respond in a variety of ways in different runs but the POC continued to cumulate until the end of the run. These changes were accompanied by a succession in the species of ciliate which was numerically dominant and there was a change-over from predominantly bacterivore to carnivore forms.Scanning electron-micrographs of the sand grain surfaces showed that the bacteria were attached by strong filaments and that apparently anaerobic fusiform bacteria appeared towards the end of a run and during periods of high temperature. The micrographs were also used to assess the efficiency of the shaking technique at removing bacteria from the sand grain surfaces.A laboratory filter model was used to perturb experimentally the simulated sand filter system by changing the filtration rates experimentally and determining the depth distributions of the ciliate fauna and bacterial flora. In general, the densities of organisms in the model filter were less than those found in lit operational beds,perhaps because of the difficulty of provding realistic levels of radiation.<p

The failure of democracy in Yemen: An analysis of external dimension

The revolution of North Yemen to step down the Imam Traditional Regime in 1962, and the independent of South Yemen from the British colony in 1967, both never produced systematic process for democracy building in their societies. The declaration of two parts Unification in 1990 represented a new shifting in the evolution of contemporary Yemen at the level of democracy building process.The newly established country adopted democracy and political pluralism, a formula that was widely adopted in many developing countries with the collapse of the Soviet Union. The constitution of The Republic of Yemen, which was amended in 1994 stated that political pluralism and multi – parties system is an essential element in the political regime. Within two decades (1990 – 2010) Yemen has witnessed many activities and programs that were considered to be steps in the process of democracy building. The elections at the parliamentary, presidential, and local levels were the explicit expression of such activities and programs. Within the events of the political crisis, that started to appear in 2006, and the failure of dialogue between the regime and the political opposition in 2010, and blow of Arab Spring winds to Yemen in the beginning of 2011, it appears clearly that democracy building strongly faced serious challenges and closing doors.Although the Gulf Cooperation Council's Initiative in Nov.2011 gave some hopes to find some outlets, and suggested what we call the transition period of two years in order to reach a presidential and parliamentary elections, the invasion of the Yemeni Capital in Sep. 2014 by Houthis militias, the cover allied between former president Salah and the Houthis militias, and the outbreak of armed extension by this militias to control the other govern orates all over the country, and hence the announcement of Zero Time to launch the Decisive Storm by the allied forces leaded by Saudi Arabia in March, 2015 to bring back the legitimate president Hadi to power, all these events stopped the process of democracy building and pushed this process to the Grand Failure Station. Within this 25 – year duration, we witnessed a very influential role of the external factors, the role exerted by the international actors such as the USA, the EU, and the UN. This paper address such influence, and focuses on the roles of the external actors at two levels: the first is the regional and superpowers, the second is the regional and international organizations

CHITOSAN NANOPARTICLES AS DRUG DELIVERY SYSTEM FOR CEPHALEXIN AND ITS ANTIMICROBIAL ACTIVITY AGAINST MULTIIDRUG RESISTENT BACTERIA

Objective: The evolution of antimicrobial resistance is a universal obstacle that necessities the innovation of more effective and safe antimicrobial alternatives with synergistic properties. The purpose of this study was to investigate the possible improvement of cephalexin antimicrobial treatments by loading into chitosan-based nanoparticles, then evaluate their antibacterial and antibiofilm activities as well as determination of its cytotoxicity. Methods: Chitosan nanoparticles (CSNPs) were prepared by ionic gelation method. Parameters were studied to optimize the particle size of CSNPs including pH, stirring rate, homogenization and ultra-sonication time. Size was measured by transmission electron microscope (TEM) and Zeta sizer, morphology seen by scanning electron microscope (SEM). Entrapment efficiency, drug loading and drug content were calculated. Stability of both plain and loaded chitosan Nano-carriers, Drug release and Kinetics also compatibilities were studied. Antimicrobial activity of CSNPs and cephalexin loaded CSNPs were evaluated against 4 Gram-positive and 4 Gram-negative standard and clinical isolates by microdilution method, also assessment of antibiofilm activity of both formulas was investigated against two biofilm producers clinical isolates by tube assay in addition to determination of their cytotoxicity by MTT(3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. Results: Chitosan nanoparticles and its loaded antibiotics proved compatible combination with small Zeta size, suitable Zeta potential, maximum EE% and drug-loading capacity, sustained controlled release properties followed diffusion kinetic model and six month stability studies. Cephalexin loaded CSNPs showed better antimicrobial activity than plain CSNPs. Synergistic effects were found against S. aureus (ATCC 25923), B. subtilis (ATCC 9372), S. epidermidis, E. faecalis, P. aeruginosa (ATCC 29853) in addition to two carbapenem resistant isolates k. pneumoniae and E. coli. Also cephalexin loaded CSNPs exhibited antibiofilm activity against E. faecalis clinical isolate. Even though, cephalexin loaded CSNPs exhibited significant antibacterial activity, it showed less toxicity against mammalian cells, it had IC50 equal to 231.893 and did not exhibit any cytotoxicity against the WI-38 fibroblast cells at concentration 23.4 µg/ml. Conclusion: Cephalexin loaded CSNPs possessed good stability and sustained release effect in addition to its antimicrobial, antibiofilm activities and reduced cytotoxicity

Correlation Between the Total Small Bowel Length and Anthropometric Measures in Living Humans : Cross-Sectional Study

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Transitional Adaptation model for facilitating technology and expertise mobilisation in Gulf AEC Organisations

The fragmented nature of the Architecture, Engineering, and Construction (AEC) industry is well recognised, the main issues of which relate to failures in communication, process, productivity and interoperability. These failures have contributed to an increased proliferation of adversarial relationships between the different parties involved in projects, the result of which have deleteriously affected projects. Challenges include a range of issues, from the veracity of design information throughout the project lifecycle, through to supply chain communication. These are global issues. For example, in the Gulf States, the nature and complexity of AEC projects has changed significantly due to increased globalisation and the emergence of enmeshed transnational practices. This has created an overwhelming reliance on the mobilisation and transfer of technology/expertise of professional expatriates, which has influenced the approach taken to traditional design and construction business models, including staff roles and procedures. New knowledge and ways of working are needed to support future projects in the Gulf States. There is also a requirement to capture and codify domain-specific expertise. This paper discusses the need to enhance Qatar’s AEC industry by fostering a smooth transition from its current position, into a more sustainable [replicable] state. The philosophical underpinnings of this paper take into account disparate socio-cultural, environmental and economic impacts of change, in terms of business models, technology, innovation, labour market needs, local laws/bylaws, and legislation. A theoretical growth model is presented for discussion. This builds on the experience of the UK (in particular) in terms of facilitating the mobility and penetration of technology/expertise/change in the AEC sectors. This paper presents a series of recommendations needed to develop a Pervasive Transnational Adaptation model for Qatar and the Gulf States, covering such issues as: ICT adoption, agile project management, technology-transfer, innovation, offsite construction, Public Private Partnerships, capacity building, and international strategic alliances