Navigation in hypermedia learning systems: Experts vs. novices

With the advancement of Web technology, hypermedia learning systems are becoming more widespread in educational settings. Hypermedia learning systems present course content with non-sequential formats, so students are required to develop learning paths by themselves. Yet, empirical evidence indicates that not all students can benefit from hypermedia learning. Research into individual differences suggests that prior knowledge has significant effects on student learning in hypermedia systems, with experts and novices showing different preferences to the use of hypermedia learning systems and requiring different levels of navigation support. It is therefore essential to develop a mechanism to help designers understand the needs of experts and novices. To address this issue, this paper presents a framework to illustrate the needs of students with different levels of prior knowledge by analyzing the findings of previous research. The overall aim of this framework is to integrate students’ prior knowledge into the design of hypermedia learning systems. Finally, implications for the design of hypermedia learning systems are discussed

Automation of electro-hydraulic routing design using hybrid artificially-Intelligent techniques

Traditional ‘simple’ genetic algorithms are theoretically capable of solving the 3-D spatial problem represented by hydraulic and electrical harness design. However, the size of the ‘solution space’ to be searched, for even the simplest of problems can represent a computational load sufficient to limit any practical application. This research proposes a ‘key-point search’ which when used prior to the GA can successfully reduce the size of the computational task. It does this by identifying those points in the physical three dimensional space which are most likely to be useful in the final solution and producing an initial population of solutions from these points. This is shown to significantly reduce computation times to find valid solutions

Electrocatalytic Activity of Electropolymerized Cobalt Tetraaminophthalocyanine Film Modified Electrode towards 6-Mercaptopurine and 2-Mercaptobenzimidazole

The electrocatalytic activity of electropolymerized cobalt tetraaminophthalocyanine (poly-CoTAPc) film modified on the glassy carbon electrode (GCE) towards 6-mercaptopurine (6MP) and 2-Mercaptobenzimidazole (MBI) was studied. Comparing with the case at the unmodified GCE, the poly-CoTAPc film decreased the overpotential of oxidation of 6MP (1.0 × 10–3 mol L–1) and MBI (1.0×10–3 mol L–1) by 335 and 189mV, respectively, and increased the peak current by about 3 and 2 times, respectively, while the reduction potential of the disulphide product of previous oxidation of 6MP shifted positively by 312 mV and the peak current increased by 40 times in 0.1 mol L–1 phosphate buffer solution (PBS, pH = 2.0). The poly-CoTAPc film exhibited efficiently electrocatalytic activity for 6MP and MBI with relatively high sensitivity, stability and long-life.Keywords: Electrocatalysis, 6-mercaptopurine, 2-mercaptobenzimidazole, Cobalt Tetraaminophthalocyanine, Electropolymeric Fil

Solution heat treatment, forming and in-die quenching of a commercial sheet magnesium alloy into a complex-shaped component: experimentation and FE analysis

Interest in lightweight materials, particularly magnesium alloys, has increased significantly with rising efficiency requirements in the automotive sector. Magnesium is the lightest available structural metal, with a density approximately 35% lower than that of aluminium. The potential is great for magnesium to become a primary material used in future low carbon vehicle structures; however, there are significant obstacles, namely low ductility and formability, particularly at room temperature. The aim of this work is to present the feasibility of using the solution Heat treatment, Forming, and in-die Quenching (HFQ) process to produce complex shapes from a sheet magnesium alloy, and to use the results to verify a simulation of the process developed using commercial FE software. Uniaxial tensile tests were initially conducted to establish the optimum parameters for forming the part. Stamping trials were then carried out using these parameters, and a simulation set up modelling the forming operation. It was shown that the HFQ process could be used to form a successful component from this alloy, and that a good match was achieved between the results of the forming experiments and the simulation.The authors gratefully acknowledge the support from the EPSRC (Grant Ref: EP/I038616/1) for TARF-LCV: Towards Affordable, Closed-Loop Recyclable Future Low Carbon Vehicle Structures

Mesoporous bioactive glass and alginate composite scaffolds for tissue engineering

Sol-gel derived, silica-based bioactive glasses of a ternary system (SiO₂ – CaO – P₂O₅) has the potential to promote hard and soft tissue regeneration. Compared to melt-derived glasses, glasses synthesised from the sol-gel process has the advantage of low processing temperatures, high specific surface areas (SSA) and tailorable porous nanostructures. Using scaffolds as a strategy for tissue engineering, the application of sol-gel derived bioactive glasses in combination with alginate polymers as scaffold composite materials has great potential and therefore requires further study. This thesis investigates the synthesis of bioactive glasses via the sol-gel (acidic) route and the multi-step (alkali) route, through the sol → drying → sintering stages. Sol-gel route nanoparticles derived were heterogeneous in shape, while the multi-step route produced spherical (30 – 90 nm diameter) nanoparticles. Increases in calcium content of the sol led to an increase in pore size and a decrease in SSA. Three dehydration methods: oven, vacuum and freeze drying were devised to control the morphology of nanoparticles. Freeze dried nanoparticles were found to have a rough surface texture, with an aligned ordered porous nanostructure. This led to faster apatite formation when compared to oven dried nanoparticles immersed in simulated body fluid (SBF). A novel internal ionic diffusion cross-linking method of alginate was developed, utilising the glass nanoparticles as nanocarriers, for the synthesis of alginate-bioactive glass composite scaffolds. Strontium chloride (SrCl₂) and copper chloride (CuCl₂), which provided therapeutic ions, were impregnated into the nanocarriers, and were compared to calcium chloride (CaCl₂), as the control. Impregnation efficiency was in the order of CuCl₂ > SrCl₂ ≈ CaCl₂, attributed to Cu²⁺ having the smallest ionic radii and its interaction with silinol groups on the nanocarrier surfaces. Scaffold gelation time was correlated to the type of cross-linking salt, its loading concentration and glass to alginate (G/A) ratio. It was observed that SrCl₂ loaded nanocarriers (BGSr) were most efficient in cross-linking when compared to CuCl₂ and CaCl₂ loaded nanocarriers (BGCu and BGCa respectively), due to Sr²⁺ having a greater affinity towards alginate. Results showed that nanocarriers with the highest SSA possessed the highest impregnation efficiency; however nanocarriers with the largest pore diameter and volume led to the fastest scaffold gelation time. BGCa and BGSr scaffolds showed significant improvements in maintaining stiffness (Young’s modulus) and shear resistance (maximum shear stress) after incubation in aqueous solutions for up to 28 days, which were in contrast to the deterioration in mechanical properties of conventional CaCl₂ cross-linked scaffolds. Calcium ions were detected in the range above 260 ppm in BGCa nanocarrier supernatant, suggesting the gradual release of ions from the nanocarriers, internally diffusing into the scaffold matrix, leading to continuous cross-linking over time. Meanwhile, in vitro biological studies showed fast apatite formation on BGCa cross-linked scaffolds in SBF, with the scaffolds capable of supporting the attachment, growth and proliferation of human osteoblast cells, thus indicating their high bioactivity. Control over glass nanoparticle morphology was achieved and through specific ionic impregnation, the successful synthesis of alginate-bioactive glass composite scaffolds was demonstrated, producing bioactive scaffolds with improved mechanical properties

Incremental anisotropic damage theory and its numerical analysis

2004-2005 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Recent progress in organic-based radiative cooling materials: fabrication methods and thermal management properties

Organic-based materials capable of radiative cooling have attracted widespread interest in recent years due to their ease of engineering and good adaptability to different application scenarios. As a cooling material for walls, clothing, and electronic devices, these materials can reduce the energy consumption load of air conditioning, improve thermal comfort, and reduce carbon emissions. In this paper, an overview is given of the current fabrication strategies of organic-based radiative cooling materials, and of their properties. The methods and joint thermal management strategies including evaporative cooling, phase-change materials, fluorescence, and light-absorbing materials that have been demonstrated in conjunction with a radiative cooling function are also discussed. This review provides a comprehensive overview of organic-based radiative cooling, exemplifying the emerging application directions in this field and highlighting promising future research directions in the field

Error, reproducibility and sensitivity : a pipeline for data processing of Agilent oligonucleotide expression arrays

Background Expression microarrays are increasingly used to obtain large scale transcriptomic information on a wide range of biological samples. Nevertheless, there is still much debate on the best ways to process data, to design experiments and analyse the output. Furthermore, many of the more sophisticated mathematical approaches to data analysis in the literature remain inaccessible to much of the biological research community. In this study we examine ways of extracting and analysing a large data set obtained using the Agilent long oligonucleotide transcriptomics platform, applied to a set of human macrophage and dendritic cell samples. Results We describe and validate a series of data extraction, transformation and normalisation steps which are implemented via a new R function. Analysis of replicate normalised reference data demonstrate that intrarray variability is small (only around 2% of the mean log signal), while interarray variability from replicate array measurements has a standard deviation (SD) of around 0.5 log2 units ( 6% of mean). The common practise of working with ratios of Cy5/Cy3 signal offers little further improvement in terms of reducing error. Comparison to expression data obtained using Arabidopsis samples demonstrates that the large number of genes in each sample showing a low level of transcription reflect the real complexity of the cellular transcriptome. Multidimensional scaling is used to show that the processed data identifies an underlying structure which reflect some of the key biological variables which define the data set. This structure is robust, allowing reliable comparison of samples collected over a number of years and collected by a variety of operators. Conclusions This study outlines a robust and easily implemented pipeline for extracting, transforming normalising and visualising transcriptomic array data from Agilent expression platform. The analysis is used to obtain quantitative estimates of the SD arising from experimental (non biological) intra- and interarray variability, and for a lower threshold for determining whether an individual gene is expressed. The study provides a reliable basis for further more extensive studies of the systems biology of eukaryotic cells

Deamidated lipocalin-2 induces endothelial dysfunction and hypertension in dietary obese mice

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