New approaches to casting hypereutectic Al-Si alloys to achieve simultaneous refinement of primary silicon and modification of eutectic silicon

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel UniversityHypereutectic Al-Si alloys are of increasing interest for applications that require a combination of light weight and high wear resistance, such as pistons, liner-less engine blocks and pumps. The wear resistance of this class of alloys is due to the presence of hard primary Si particles formed during casting. The objective of this work was to develop one or more methods of refining primary silicon in cast hypereutectic Al-Si alloys to compete with the conventional process of adding phosphorous and to achieve the simultaneous modification of silicon in the Al-Si eutectic. A robust sampling/casting technique was developed to minimise macro-segregation of primary silicon during solidification of hypereutectic Al-Si alloys by using water cooled steel mould with cooling rate in excess of 15 K/s. The morphology of silicon phases was found to change with increasing melt temperature and cooling rate. The high cooling rate and superheat temperature produces a good distribution of polyhedral primary silicon particles in a refined lamellar eutectic matrix in solidification of commercial purity Al-Si alloys. Removing Ca by fluxing with K2SiF6 prior to casting can improve the refinement and modification effect of Mg and Sb respectively. Effects of various inoculants were studied. Microstructural analysis showed that Mg and ZnS refined primary Si whereas MgO, CaO and Na2S coarsened the primary Si together with a modification effect on the eutectic Si. Adding Zn had no effect on morphology of Si phases. Refinement of both primary and eutectic silicon phases was observed for the Al-15Si alloy with Mg content ≤ 0.3 wt%. P-doped γ-Al2O3 was found to be a potent substrate to nucleate primary silicon whilst good modification of the eutectic matrix is retained during solidification of hypereutectic Al-Si alloys. On using P-doped γ-Al2O3 could be a perfect and clean source of P without additional impurities. A new solid-liquid duplex casting process was devised to achieve simultaneous refinement and modification of Si phases in hypereutectic Al-Si alloys with improvement in mechanical properties. The static mechanical properties of Al-Si produced by the solid-liquid duplex casting process are significantly better than conventionally cast untreated Al-Si and slightly better than conventionally cast Al-Si treated with P and/or Sr. A novel Al-ZnS master alloy was developed by in situ reaction of Zn and Na2S in the Al melt. The results from this study leave little doubt that this novel Al-ZnS master alloy is a promising refiner in solidification of hypereutectic Al-Si alloys. It refines primary silicon to the same extent as that achieved by adding P via Cu-P following the same refinement mechanism.EPSRC,U

Toward the impacts of Indian drama serials on Bangladeshi family system: an overview of people’s perception

Nowadays Indian drama serials are very popular in Bangladesh. Young, old even children are interested to watch it. These people watch and imitate the life style portrayed in these daily soaps. That is gradually eating up our traditional and enriched cultural norms and values. Study revealed that these Indian drama serials provoke sexual behavior, instigate pre and extra martial affair, educate criminal activity, originate eve teasing, and nurture conflict between family members. Study also disclosed that these daily soaps impose Hinduism culture in every sphere of life of Bangladeshi people. This study was carried on 100 families of Dhaka city corporation area on the basis of random sampling. At the end the paper suggested some remedial measures that are indispensably needed to save our viewers from the negative consequences of Indian drama serials and stop cultural intrusion

The use of isoenzymes in the study of germination, development and breeding of legumes

Amylase activities and patterns were compared in extracts from mature seeds and from different parts of seedlings at various stages of seed germination of various varieties of different legume species. Apart from soyabean, all varieties had low levels of amylase activities in extracts from mature seeds, while the former had a remarkably high level. Amylase activities and the number of bands increased during seed germination and showed time and tissue specifity. The extracts from cotyledons had the highest activities and the largest number of bands as compared to that of the various parts of embryonic axes. Amylase activities and patterns had time specific changes during the various stages of seed development of the 7 varieties of different legume species studied. All the different varieties showed changes in zymogram patterns and decreased amylase activity during seed development, except soyabean where amylase activity remained high at all stages. The different components of amylase were characterised in pea (var. Feltham First). One band of a -amylase activity, restricted to the cotyledons, was present in the middle stages of seed development only, then reappeared at the third day of seed germination. The embryonic axes β -amylase activity decreased as the seed developed, to reach zero level in mature seeds, and reappearred during seed germination. The reverse sequence occurred for the cotyledonary β -amylase. The pea a -amylase was partially purified using ethanol precipitation, glycogen complex and hydroxyapatite column chromatography. The purified protein had three major bands with few faint bands on the SDS polyacrylamide gel. The embryonic axes β -amylase of pea was partially purified using the conventional method, ammonium sulphate precipitation, ion exchange chromatography and gel filtration. The purified protein contained two thick bands and many faint bands on the SDS polyacrylamide gel. The zymogram patterns of phosphorylase, EST, GDH, GOT, LDH, ADH and MDH were investigated during seed development of various varieties of different legume species. The most noticeable changes as the seeds developed were the decrease in activities and number of bands of EST in pea and soyabean, shift in GDH activities between isoenzyme forms in pea (var. English Wonder), increase in GDH activities and number of bands in dwarf French bean and soyabean and increase in activities and number of bands of MDH in pea (var. Feltham First)

Magnetic Field Treatment to Control Scale Growth and Oxygen Scavenger Performance in Mono Ethylene Glycol Regeneration Process

Magnetic fields application is gaining increased importance in all areas of industry, this includes physical and chemical applications. Even though these have excellent prospects, it is not understood whether magnetic fields treatment can work efficiently at MEG regeneration systems in oil and natural gas industries. Magnetic fields applications, the focus of this study, proposes non-chemical techniques to control scale (CaCO3) formation growth and oxygen contamination after conventional approaches have been exhausted

Streaming Feature Grouping and Selection (Sfgs) For Big Data Classification

Real-time data has always been an essential element for organizations when the quickness of data delivery is critical to their businesses. Today, organizations understand the importance of real-time data analysis to maintain benefits from their generated data. Real-time data analysis is also known as real-time analytics, streaming analytics, real-time streaming analytics, and event processing. Stream processing is the key to getting results in real-time. It allows us to process the data stream in real-time as it arrives. The concept of streaming data means the data are generated dynamically, and the full stream is unknown or even infinite. This data becomes massive and diverse and forms what is known as a big data challenge. In machine learning, streaming feature selection has always been a preferred method in the preprocessing of streaming data. Recently, feature grouping, which can measure the hidden information between selected features, has begun gaining attention. This dissertation’s main contribution is in solving the issue of the extremely high dimensionality of streaming big data by delivering a streaming feature grouping and selection algorithm. Also, the literature review presents a comprehensive review of the current streaming feature selection approaches and highlights the state-of-the-art algorithms trending in this area. The proposed algorithm is designed with the idea of grouping together similar features to reduce redundancy and handle the stream of features in an online fashion. This algorithm has been implemented and evaluated using benchmark datasets against state-of-the-art streaming feature selection algorithms and feature grouping techniques. The results showed better performance regarding prediction accuracy than with state-of-the-art algorithms

An Examination Of Residents’ Attitudes Toward Tourism Development: The Case Of Aqaba In Jordan

Generally, the economic contribution of tourism is the most highly researched field in terms of tourism impacts on host communities. Nevertheless, social and cultural changes in host communities should have equal attentions by scholars and official planners when designing tourism policies and strategies. To measure how community members perceive tourism impacts, theoretical foundations and a set of predictors were used. Social exchange was one of the first social theories that have been used for this purpose. Based on the contradictory results in many previous studies that used this theory, it was found that using a single theory does not lead to meaningful findings. Accordingly, the current study is an attempt to develop a new model based on Perdue et al’s (1990) model. This theoretical model consists of social exchange theory (SET) and power theory. Six main hypotheses were tested to point out the relationship between the independent variables (a set of predictor factors, power, and SET) and the dependent variable (residents’ support for tourism). The moderation relationship of power and SET was also examined in order to explain this relationship in other conditions; this is a way to explain possible contradictory results concerning the relationships between predictor factors and attitudes. Based on the quantitative results, significant relationships were found between all the independent variables and support for tourism

Effect of Culturing Time and Hormonal Combinations on Organogenesis of Date Palm (Phoenix dactylifera L., CV. Khnazi) In Vitro

Date palm (Phoenix dactylifera L.) monocotyledon dioecious tree is one of the most important fruit crop trees in the Arabian Gulf region in general and in the UAE in particular. Date palm is propagated sexually by seeds or vegetative by offshoots. Seed propagation is not appropriate for commercial production because of the high genetic heterozygosity, which resulted in not true-to-type male and female seedlings. The vegetative propagation utilizing offshoots is slow and inefficient for rapidly growing demands of the date industry. Therefore, it seems essential to use plant tissue culture techniques for propagating and producing date palms. The present study included three experiments that were conducted through three successive seasons (1996- 1998). The first experiment included the effect of 18 different media developed from various combinations of different auxin and concentrations, in addition to the control (no hormones at all), on shoot bud generation from shoot tip of Khnazi cultivar. Maximum percentage of explants formed bud generative tissue were induced by the addition of 1.6mg/l lAA or 0.4mg/l of both lAA and NAA to the initiation medium. Maximum number of differentiated buds per bud generative tissue resulted from the addition of 0.8 mg/l lAA to initiation medium. The initiation medium contained Murashige and Skoog inorganic salts and supplemented with 100mg/l myo-inositol, 0.5mg/l nicotinic acid, 0.5 mg/l pyridoxine, 0.1 mg/l thiamine-HCI, 2 mg/l Glycine, 40mg/l adenine sulfate, 2g/l polyvinile pyrolidon (PVP 40000), 3mg/l activated charcoal, and 40mg/l sucrose. In the second experiment, 23 different media were developed from the combinations of different cytokines and concentrations. Maximum percentage of explants formed bud generative tissue was induced by the addition of 3.2 mg/l 2iP or 1.6 mg/l BAP. Maximum number of generated buds per explants was induced by the addition of 3.2 mg/l 2iP to initiation medium. Both auxins and cytokines proved to be essential for the induction of bud generative tissue and for differentiation of shoot buds from cultured explants. In the third experiment, shoot tips of the tested cultivar were cultured monthly beginning from September 5, and continued for successive 12 months, on two different types of medium. Maximum percentage of explants formed bud generative tissue was attained during spring season, especially in March. Similarly, maximum number of buds was produced during the spring, and in particular at the month of April regardless of medium types. The hot environment in summer inhibited the formation bud generative tissues, and the differentiation of shoot bud per generative tissue

Optimal control of diabetes

This thesis considers optimal control problems related to one of the major global health problems, Diabetes. We adopt a comprehensive dynamic model of the blood glucose regulatory system and show how it can be readily fitted to individuals. Based on this, we develop a composite dynamic model for simulating the effects of exercise and subcutaneous insulin injections on the blood glucose regulatory system. We then determine that optimal treatment regimens on the basis of the composite model

Responses of plastic shading nets to global and diffuse PAR transfer: Optical properties and evaluation

AbstractTo cover agricultural structures for protecting plants from high solar radiation in hot and sunny regions different types of shading nets are used. In summer, the amount of photosynthetically active radiation (PAR) transmitted through these nets usually fulfils plant growth requirements. However, their applicability in winter is still unknown. So far, the choice of nets has mostly been empirical, because technical data such as the radiometric properties that are used to characterize the different types of nets are not available. This paper presents a simple method for measuring the radiometric properties related to global and diffuse PAR of seven types of shading nets including nets with colours and shading rates that are commonly used in hot regions. A shading system was developed to simulate the diffuse PAR under cloudy conditions. The results show that under clear sunny and cloudy conditions the radiometric properties depended on both net porosity and colour. Net reflectance strongly depended on net colour. Net transmittance and absorptance depended primarily on colour and secondarily on porosity. The radiometric properties of nets under global and diffuse PAR conditions tended to be similar to those of translucent materials so that a plastic net can be considered as translucent material when investigating the equivalent optical parameters (refractive index and absorption coefficient). This can help to predict the radiometric properties of the net without the need of measurements. Under the sunny conditions of winter seasons, the structures covered with the tested nets are suitable for growing crops that can grow at PAR less than 150Wm−2. However, under cloudy conditions very few plants will grow that can grow at PAR less than 30Wm−2

Refinement of primary Silicon crystals by novel Al-ZnS master alloy in solidification of Hypereutectic Al-Si Alloys

A novel Al-ZnS master alloy was developed by in situ reaction of Zn and Na2S in the Al melt. The results from this study left little doubt that this novel Al-ZnS master alloy was a promising refiner in solidification of hypereutectic Al-Si alloys. It refined the primary silicon to the same extent as that achieved by adding P via Cu-P following the same refinement mechanism. The SEM work confirmed that there were many pre-formed ZnS particles contained in the master alloy. The optical metallography showed that the morphologies of the primary silicon crystals in the solidified Al-22Si alloy were drastically changed from irregular coarse morphology to fine regular particles. The primary silicon crystal was refined from 74 m to 26, 22, 24 m by adding 0.05, 0.1, 0.15 wt% ZnS respectively with holding time of 20 min, where as the average particle size of the primary silicon refined by 200 ppm P reduced to 20 m. With the increase of the holding time up to 1.5 hr, the primary silicon size will increase up to 33 m in adding 0.1 wt% ZnS