Maximum power point tracking for variable-speed fixed-pitch small wind turbines

Variable-speed, fixed-pitch wind turbines are required to optimize power output performance without the aerodynamic controls. A wind turbine generator system is operated such that the optimum points of wind rotor curve and electrical generator curve coincide. In order to obtain maximum power output of a wind turbine generator system, it is necessary to drive the wind turbine at an optimal rotor speed for a particular wind speed. In fixed-pitch variablespeed wind turbines, wind-rotor performance is fixed and the restoring torque of the generator needs to be adjusted to maintain optimum rotor speed at a particular wind speed for maximum aerodynamic power output. In turbulent wind environment, control of wind turbine systems to continuously operate at the maximum power points becomes difficult due to fluctuation of wind speeds. Therefore, special emphasis is given to operating at maximum aerodynamic power points of wind rotor. In this paper, the performance of a Fuzzy Logic Maximum Power Point Tracking (MPPT) controller is investigated for applications on variable-speed fixed-pitch small- scale wind turbines

A review of test protocols for assessing coating performance of water ballast tank coatings

Concerns on corrosion and effective coating protection of double hull tankers and bulk carriers in service have been raised especially in water ballast tanks (WBTs). Test protocols/methodologies specifically that which is incorporated in the International Maritime Organisation (IMO), Performance Standard for Protective Coatings for Dedicated Sea Water ballast tanks (PSPC) are being used to assess and evaluate the performance of the coatings for type approval prior to their application in WBTs. However, some of the type approved coatings may be applied as very thick films to less than ideally prepared steel substrates in the WBT. As such films experience hygrothermal cycling from operating and environmental conditions, they become embrittled which may ultimately result in cracking. This embrittlement of the coatings is identified as an undesirable feature in the PSPC but is not mentioned in the test protocols within it. There is therefore renewed industrial research aimed at understanding this issue in order to eliminate cracking and achieve the intended coating lifespan of 15 years in good condition. This paper will critically review test protocols currently used for assessing and evaluating coating performance, particularly the IMO PSPC

Drilling oil-based mud waste as a resource for raw materials: a case study on clays reclamation and their application as fillers in polyamide 6 composites.

To convert the hazardous oil-based mud waste into a resource, this study has addressed reclaimed nanoclays and its application as a filler material for reinforcing polyamide 6 polymer matrix into a novel polymer composite material. This work focuses on the synergistic effect of complex mixture of various clay minerals reclaimed from oil-based mud waste on different mechanical properties in polyamide-6 (PA6)/oil-based mud fillers (OBMFs) nanocomposites. PA6/OBMFs nanocomposites were manufactured through the melt compounding of OBMFs with PA6 in a twin-screw extruder followed by injection moulding. The study shows significant improvement for mechanical properties. For instance, the tensile properties increased with the incremental loadings of OBMFs in PA6 matrix. The Young’s moduli were increased by 42% and 35% in PA6 with 7.5 and 10 wt% OBMFs nanocomposites respectively whereas the tensile strengths were increased by 24% and 16% in PA6 with 7.5 and 10 wt% OBMFs nanocomposites respectively. The flexural strength increased by 26% with the addition of OBMFs from 0 to 10 wt% in PA6. The storage modulus of the nanocomposite containing 10 wt% OBMFs was 16% higher than the storage modulus of neat PA6 at 30° C, whereas at 60° C (glass transition temperature, Tg of neat PA6) the storage modulus of PA6 with 10 wt% OBMFs was 56% higher than that of neat PA6. The study shows that the oil-based mud waste can be appropriately management to develop a new raw materials resource for polymer technology

High temperature corrosion studies and interdiffusion modelling in TiAl based alloys coated with high performance surface layers

This work forms a part of a large EU project (InnovaTiAl) designed to increase the service temperature (up to 1273 K) of TiAl based intermetallics (Ti45Al8Nb) coated with high performance surface layers for applications in power generation and also in aerospace components. In this thesis the high temperature corrosion behaviour of some of these newly developed high performance coatings deposited on Ti45Al8Nb alloys using UBM and HIPIMS/UBM has been studied. The coatings studied included intermetallic coatings: TiAlCr, TiAlCrY, Al2Au, and ceramic coatings: CrAl2%YN, TiAlYN/CrN+Al2O3, TiAlN+Al2O3, CrAlYN/CrN+CrAlYON coated Ti45Al8Nb etched by Cr, CrAlYN/CrN+CrAlYON coated Ti45Al8Nb etched by CrAl, CrAlYN/CrN+CrAlYON coated Ti45Al8Nb etched by Y, CrAlYN/CrN coating Y etch, CrAl (thin), CrAlYN/CrN coating Cr etch, CrAl (thin), CrAlYN/CrN coating, Y etch, CrAlY (thick) coated Ti45Al8Nb. High temperature corrosion investigations were carried out by the exposing the coated materials in oxidising (static air, pO2 = 21278.25 Pa), sulphidising (pS2 = 10-1 Pa, and pO2 = 10-18 Pa) and hot corrosion (20%NaCl/80%Na2SO4) environments at temperatures range 1023 – 1223 K. The long term oxidation studies have been performed up to 5000 hours at 1023 K. Weight change data have been used to determine the corrosion kinetics. SEM studies have provided information on morphology; EDS analyses have given the information on concentration profiles and phase contents have been obtained by XRD analyses. The excellent high temperature oxidation resistance has been achieved for the CrAl2%YN coating at temperature rage 1023 – 1123 K for 500 hours. Also TiAlCr and TiAlCrY have shown moderate degree of corrosion resistance in oxidising environment after 500 hours of exposure at temperature range 1023 – 1223 K. The sulphidation experiments for 1000 and 675 hours at 1023 K and 1123 K respectively showed that the uncoated material developed a multilayered thick scale with poor resistance to sulphidation. The ceramic coatings developed a good protective Al2O3/Cr2O3 on places where the coatings remained intact and did not undergo cracking. However due to the cracks in the top coat, the development of non protective TiO2 occurred at 1023 and 1123 K. Hot corrosion studies performed at 1023 K for 150 hours under this thesis showed that all exposed materials (CrAl2%YN, TiAlN+Al2O3, and TiAlYN/CrN+Al2O3) suffered uneven attacks (crack formation, spallation, and the lack of Al2O3 formation). Interdiffusion studies of mass transport have been performed by GDM on TiAlCrY coated alloy after 500 hours oxidation at 1023 and 1123 K. A reasonable degree of agreement between the experimental and the simulated profiles has been achieved.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Optimisation of vertical axis wind turbines

A practical Vertical Axis Wind Turbine (VAWTs) based on a Darrieus rotor has been designed and tested and found to be capable of self-starting at wind speeds above 4m/s. The self-start feature has been achieved by replacing the usual symmetrical aerofoil blade in the VAWT rotor and by using a concentric Savonius rotor or semi-cylinder turbine. A computer program was produced to compute the power coefficient versus tip speed ratio characteristics of a selected aerofoil profile employed in a VAWT. The program accounts for chord length, pitch angle, number of blades, and rotor radius at any wind speed. The published data from 40 aerofoil sections were assessed, taking into account the two main criteria — self-starting and efficiency. Computational fluid dynamics software (ANSYS, Flotran) has been used to investigate the lift and drag performance of a NACA 66-212 and NACA 4421 aerofoils in order to check the computer program predictions. Excellent agreement was obtained for the static aerofoil assessment, but only after special ICEM Computational Fluid Dynamics (CFD) meshing interface routines were utilised. However, agreement between the theoretical and published results was not good for the rotating aerofoils in a VAWT. Thus, further CFD work was not pursued and in preference, an experimental route was initiated. In the first series of wind tunnel tests involving three candidate profiles, good agreement was found between the experimental results and the mathematical models. The aerofoils chosen were the NACA 661-212, the 51223 and the Clark-Y standard aerofoils. A number of prototype VAWTs were fabricated and tested for the influence of the blade pitch angle, the chord length ratio, with 2 or 3 blades. The aerofoil surfaces were made from aluminium sheet with a standard surface finish. The prototype designs were tested in the Northumbria University low speed wind tunnel facility - the models were 0.4 m. high with a 0.4 m diameter. The torque versus wind speed characteristics were recorded and analysed. The S 1223 profile was found to be self-starting with high efficiency. This model generated a high power coefficient of about 0.3 at a tip speed ratio of 1.2. The second series of tests were carried out in field sites in the UK with a 2 m diameter straight—bladed Darrieus rotor prototype with 3 blades using the S1223 blade section. Three field trials were undertaken in the UK to produce realistic performance characteristics for wind conditions of 4-10 m/s. The maximum power coefficient of this machine was found to be 0.18 at a tip speed ratio of 1.2. In addition, an alternative semi-cylinder turbine combined with a Darrieus rotor was fabricated and tested in the UK. It demonstrated the advantage that it could self-start at lower wind speeds, that is 3m/s but delivers approximately 50% less power than that obtained from the first proposed design. A final phase of testing was carried out with an enlarged and modified 3 m diameter prototype installed at a shrimp farm in Thailand to demonstrate how the unit could be used to replace an equivalent 2 HP 2-stroke diesel engine and hence eliminate its inherent emission pollution problems. A Savonius rotor was fitted to the prototype to improve self-start capabilities at a wind speed of 4 m/s for a practical application which by its nature required a high starting torque. The designs are easy to fabricate, low cost, pollution free and have been demonstrated to be ideal for applications in developing countries where there are sufficient wind resources.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Oil-based mud waste as a filler material in LDPE composites: evaluation of mechanical properties.

Traditionally, the drilling waste generated in oil and gas exploration operations, including spent drilling fluid, is disposed of or treated by several methods, including burial pits, landfill sites and various thermal treatments. This study investigates drilling waste valorisation and its use as filler in polymer composites. The effect of the poor particle/polymer interfacial adhesion bonding of the suspended clay in oil-based mud (OBM) slurry and the LDPE matrix is believed to be the main reason behind the poor thermo-mechanical and mechanical properties of low-density polyethylene (LDPE)/OBM slurry nanocomposites. The thermo-mechanical and mechanical performances of LDPE)/OBM slurry nanocomposites without the clay surface treatment and without using compatibilizer are evaluated and discussed. In our previous studies, it has been observed that adding thermally treated reclaimed clay from OBM waste in powder form improves both the thermal and mechanical properties of LDPE nanocomposites. However, incorporating OBM clay in slurry form in the LDPE matrix can decrease the thermal stability remarkably, which was reported recently, and thereby has increased the interest to identify the mechanical response of the composite material after adding this filler. The results show the severe deterioration of the tensile and flexural properties of the LDPE/OBM slurry composites compared to those properties of the LDPE/MMT nanocomposites in this study. It is hypothesised, based on the observation of the different test results in this study, that this deterioration in the mechanical properties of the materials was associated with the poor Van der Waals force between the polymer molecules/clay platelets and the applied force. The decohesion between the matrix and OBM slurry nanoparticles under stress conditions generated stress concentration through the void area between the matrix and nanoparticles, resulting in sample failure. Interfacial adhesion bonding appears to be a key factor influencing the mechanical properties of the manufactured nanocomposite materials

A mixed-methods study on toilet hygiene practices among Chinese in Hong Kong.

BACKGROUND: Public toilets are a common transmission vector of infectious diseases due to environmental contamination. Research on Chinese people's hygiene practices in public lavatories are lacking. This study examined Chinese people's hygiene practices in public lavatories in Hong Kong. METHODS: We conducted qualitative interviews and a self-administered questionnaire survey with local residents from June 2016 to April 2018. Four focus group discussions and three individual interviews informed the design of the questionnaire. We recruited interviewees and survey respondents via social service centers. The interviews and questionnaire focused on the public's daily practices and hygiene behaviors in public toilets. Content analysis of qualitative data was conducted. Multivariable logistic regressions were used to examine the association between age and toilet hygiene behaviors. RESULTS: Our qualitative component revealed a range of handwashing practices, from not washing at all, washing without soap, to washing for a longer time than instructions. Other toilet use practices were identified, such as not covering toilet lid before flushing and stepping on toilet seats due to dirtiness, and spitting into toilet bowls or hand basin. Totally, 300 respondents completed the questionnaire. Among them, 212 (70.9%) were female and 246 (86.1%) were aged 65 or below. More than two thirds always washed hands with soap (68.7%) and dried hands with paper towels (68.4%). Up to 16.2% reported stepping on toilet seats and 43.9% never covered the toilet lid before flushing. Over one fourth (26.4%) spit into squat toilets/ toilet bowl. Regression analyses showed that the elderly group were less likely to report stepping on toilet seats (adjusted odds ratio, AOR = 0.17, 95%CI 0.03-0.88), flushing with the toilet lid closed (AOR = 0.40, 0.16-0.96), but more likely to spit into squat toilets/ toilet bowl (AOR = 4.20, 1.50-11.74). CONCLUSIONS: Hong Kong Chinese's compliance to hygiene practices in public toilets is suboptimal. Stepping on toilet seat is a unique Chinese practice due to the dirtiness of toilet seats. Spitting practices may increase the risk of airborne infectious diseases and need improvement. Measures are needed to improve toilet hygiene behaviors, including public education campaigns and keeping toilet environment clean

ITGAM is associated with disease susceptibility and renal nephritis of systemic lupus erythematosus in Hong Kong Chinese and Thai

ITGAM was recently found to be associated with systemic lupus erythematosus (SLE) in populations of not only European ancestry, but also in Hispanic- and African-Americans, Mexicans and Colombians. The risk alleles in the gene, however, were found to be monomorphic in two Asian populations examined: Japanese and Korean. In this study, using a collection of 910 SLE patients and 2360 controls from Chinese living in Hong Kong, analyzed by both genome-wide association and direct sequencing, we confirmed the association of the same risk alleles in ITGAM with the disease. These findings were further replicated in the Thai population with 278 patients and 383 ethnicity- and geography-matched controls. Subphenotype stratification analyses showed significantly more involvement of the gene in patients with renal nephritis and neurological disorders. Although our results support a pivotal role by rs1143679 (R77H) in disease association, our data also suggests an additional contribution from rs1143683, another non-synonymous polymorphism in this gene (A858V). Therefore, despite the low-allele frequencies of the risk alleles of the gene in our two Asian populations, ITGAM was confirmed to be a risk factor related to disease susceptibility and probably severe manifestations of SLE

Pharmaceuticals in tap water: human health risk assessment and proposed monitoring framework in China

Background: Pharmaceuticals are known to contaminate tap water worldwide, but the relevant human health risks have not been assessed in China. Objectives: We monitored 32 pharmaceuticals in Chinese tap water and evaluated the life-long human health risks of exposure in order to provide information for future prioritization and risk management. Methods: We analyzed samples (n = 113) from 13 cities and compared detected concentrations with existing or newly-derived safety levels for assessing risk quotients (RQs) at different life stages, excluding the prenatal stage. Results: We detected 17 pharmaceuticals in 89% of samples, with most detectable concentrations (92%) at < 50 ng/L. Caffeine (median-maximum, nanograms per liter: 24.4-564), metronidazole (1.8-19.3), salicylic acid (16.6-41.2), clofibric acid (1.2-3.3), carbamazepine (1.3-6.7), and dimetridazole (6.9-14.7) were found in ≥ 20% of samples. Cities within the Yangtze River region and Guangzhou were regarded as contamination hot spots because of elevated levels and frequent positive detections. Of the 17 pharmaceuticals detected, 13 showed very low risk levels, but 4 (i.e., dimetridazole, thiamphenicol, sulfamethazine, and clarithromycin) were found to have at least one life-stage RQ ≥ 0.01, especially for the infant and child life stages, and should be considered of high priority for management. We propose an indicator-based monitoring framework for providing information for source identification, water treatment effectiveness, and water safety management in China. Conclusion: Chinese tap water is an additional route of human exposure to pharmaceuticals, particularly for dimetridazole, although the risk to human health is low based on current toxicity data. Pharmaceutical detection and application of the proposed monitoring framework can be used for water source protection and risk management in China and elsewhere

Genome-Wide Association Study in Asian Populations Identifies Variants in ETS1 and WDFY4 Associated with Systemic Lupus Erythematosus

Systemic lupus erythematosus is a complex and potentially fatal autoimmune disease, characterized by autoantibody production and multi-organ damage. By a genome-wide association study (320 patients and 1,500 controls) and subsequent replication altogether involving a total of 3,300 Asian SLE patients from Hong Kong, Mainland China, and Thailand, as well as 4,200 ethnically and geographically matched controls, genetic variants in ETS1 and WDFY4 were found to be associated with SLE (ETS1: rs1128334, P = 2.33×10−11, OR = 1.29; WDFY4: rs7097397, P = 8.15×10−12, OR = 1.30). ETS1 encodes for a transcription factor known to be involved in a wide range of immune functions, including Th17 cell development and terminal differentiation of B lymphocytes. SNP rs1128334 is located in the 3′-UTR of ETS1, and allelic expression analysis from peripheral blood mononuclear cells showed significantly lower expression level from the risk allele. WDFY4 is a conserved protein with unknown function, but is predominantly expressed in primary and secondary immune tissues, and rs7097397 in WDFY4 changes an arginine residue to glutamine (R1816Q) in this protein. Our study also confirmed association of the HLA locus, STAT4, TNFSF4, BLK, BANK1, IRF5, and TNFAIP3 with SLE in Asians. These new genetic findings may help us to gain a better understanding of the disease and the functions of the genes involved