8 resultados para screw retention
em Aston University Research Archive
Resumo:
This paper focusses on attracting and retaining young people into technical disciplines. It introduces a new model of technical education from age 14 that the UK Government initiated in 2008. A concept of University led Technical Colleges (UTCs) for 14-19 year olds. These state supported schools, sponsored by a University, have technical curricula, technologically enabled learning environments and strong engagement with employers. As new schools they have been able to recruit outstanding staff that are conversant with the use of technology to enhance learning and all students have their own iPads. The Aston University Engineering Academy opened in September 2012 and a recent survey of staff, students and parents has provided both qualitative and quantitative data on the benefits to motivation and learning of these embedded iPads. The devices have also had advantages for the management of data on student achievement from a leadership, teaching staff and parental view point.
Resumo:
Grafting of antioxidants and other modifiers onto polymers by reactive extrusion, has been performed successfully by the Polymer Processing and Performance Group at Aston University. Traditionally the optimum conditions for the grafting process have been established within a Brabender internal mixer. Transfer of this batch process to a continuous processor, such as an extruder, has, typically, been empirical. To have more confidence in the success of direct transfer of the process requires knowledge of, and comparison between, residence times, mixing intensities, shear rates and flow regimes in the internal mixer and in the continuous processor.The continuous processor chosen for the current work in the closely intermeshing, co-rotating twin-screw extruder (CICo-TSE). CICo-TSEs contain screw elements that convey material with a self-wiping action and are widely used for polymer compounding and blending. Of the different mixing modules contained within the CICo-TSE, the trilobal elements, which impose intensive mixing, and the mixing discs, which impose extensive mixing, are of importance when establishing the intensity of mixing. In this thesis, the flow patterns within the various regions of the single-flighted conveying screw elements and within both the trilobal element and mixing disc zones of a Betol BTS40 CICo-TSE, have been modelled using the computational fluid dynamics package Polyflow. A major obstacle encountered when solving the flow problem within all of these sets of elements, arises from both the complex geometry and the time-dependent flow boundaries as the elements rotate about their fixed axes. Simulation of the time dependent boundaries was overcome by selecting a number of sequential 2D and 3D geometries, used to represent partial mixing cycles. The flow fields were simulated using the ideal rheological properties of polypropylene and characterised in terms of velocity vectors, shear stresses generated and a parameter known as the mixing efficiency. The majority of the large 3D simulations were performed on the Cray J90 supercomputer situated at the Rutherford-Appleton laboratories, with pre- and postprocessing operations achieved via a Silicon Graphics Indy workstation. A mechanical model was constructed consisting of various CICo-TSE elements rotating within a transparent outer barrel. A technique has been developed using coloured viscous clays whereby the flow patterns and mixing characteristics within the CICo-TSE may be visualised. In order to test and verify the simulated predictions, the patterns observed within the mechanical model were compared with the flow patterns predicted by the computational model. The flow patterns within the single-flighted conveying screw elements in particular, showed good agreement between the experimental and simulated results.
Resumo:
The immunostimulatory capacities of cationic liposomes are well-documented and are attributed both to inherent immunogenicity of the cationic lipid and more physical capacities such as the formation of antigen depots and antigen delivery. Very few studies have however been conducted comparing the immunostimulatory capacities of different cationic lipids. In the present study we therefore chose to investigate three of the most well-known cationic liposome-forming lipids as potential adjuvants for protein subunit vaccines. The ability of 3ß-[N-(N',N'-dimethylaminoethane)carbomyl] cholesterol (DC-Chol), 1,2-dioleoyl-3-trimethylammonium propane (DOTAP), and dimethyldioctadecylammonium (DDA) liposomes incorporating immunomodulating trehalose dibehenate (TDB) to form an antigen depot at the site of injection (SOI) and to induce immunological recall responses against coadministered tuberculosis vaccine antigen Ag85B-ESAT-6 are reported. Furthermore, physical characterization of the liposomes is presented. Our results suggest that liposome composition plays an important role in vaccine retention at the SOI and the ability to enable the immune system to induce a vaccine specific recall response. While all three cationic liposomes facilitated increased antigen presentation by antigen presenting cells, the monocyte infiltration to the SOI and the production of IFN-? upon antigen recall was markedly higher for DDA and DC-Chol based liposomes which exhibited a longer retention profile at the SOI. A long-term retention and slow release of liposome and vaccine antigen from the injection site hence appears to favor a stronger Th1 immune response.
Resumo:
A collection of peer reviewed papers focusing on effective practice in higher education
Resumo:
With the demand for engineering graduates at what may be defined as an unprecedented high, many universities find themselves facing significant levels of student attrition-with high "drop-out levels" being a major issue in engineering education. In order to address this, Aston University in the UK has radically changed its undergraduate engineering education curriculum, introducing capstone CDIO (Conceive, Design, Implement, Operate) modules for all first year students studying Mechanical Engineering and Design. The introduction of CDIO is aimed at making project / problem based learning the norm. Utilising this approach, the learning and teaching in engineering purposefully aims to promote innovative thinking, thus equipping students with high-level problem-solving skills in a way that builds on theory whilst enhancing practical competencies and abilities. This chapter provides an overview of an Action Research study undertaken contemporaneously with the development, introduction, and administration of the first two semesters of CDIO. It identifies the challenges and benefits of the approach and concludes by arguing that whilst CDIO is hard work for staff, it can make a real difference to students' learning experiences, thereby positively impacting retention. © 2012, IGI Global.
Resumo:
Poster. Introduction: One in five menand one half of women over the age of 50 will experience a bone fracture, whichis frequently accompanied by poor bone health. This combination of poor bonehealth and fracture is a two edge sword, because not only does poor bone healthmake fractures more likely, it also reduces the efficacy of standard fracturetreatments. Currently available surgical fixation devices that were originallydeveloped for healthy bone, such as pins, plates and bone screws, are often noteffective for patients with osteoporosis, resulting in unsatisfactory outcomesor longer and more painful recovery times. One major issue is the design ofbone screws, which can loosen or pull-out from osteoporotic bone. Osteopenicscrews with larger outer thread diameters have been developed to try andaddress this problem. The larger diameter screws have been shown to be 60–70 %stronger in lab tests of individual screws but the larger diameter screwscannot be used with the standard spacing in fixation plates without the risk ofcausing fractures between the screws. In addition, many fractures occur nearjoints where there is not room to increase the spacing between screws.Therefore, new bone screws are needed for treatment of fractures in osteoporoticbone. Materials and Methods: Afterdeveloping a novel bone screw design, we fabricated screws using rapidprototyping methods. Screws were inserted into 10 pcf density sawbones polyurethanefoam as a model for osteoporotic bone. Pull-out tests were conducted using theprototype bone screw design and the standard screw design for comparison inaccordance with ASTM 543-13. Results and Discussion: Ourprototype screws have the same outer diameter as standard bone screws, but haveoptimised threads. For pull-out tests in 10 psf density sawbones poly-urethanefoam, the prototype screw design was 60 % stronger than the standard bone screwdesign (p<0.01). Conclusion: Our novel bonescrew design provides significant improvement in standard tests with syntheticbone material. Additional tests are needed to determine if the bone screwswould be suitable for human trials.
Resumo:
Social exchange theory and notions of reciprocity have long been assumed to explain the relationship between psychological contract breach and important employee outcomes. To date, however, there has been no explicit testing of these assumptions. This research, therefore, explores the mediating role of negative, generalized, and balanced reciprocity, in the relationships between psychological contract breach and employees’ affective organizational commitment and turnover intentions. A survey of 247 Pakistani employees of a large public university was analyzed using structural equation modeling and bootstrapping techniques, and provided excellent support for our model. As predicted, psychological contract breach was positively related to negative reciprocity norms and negatively related to generalized and balanced reciprocity norms. Negative and generalized (but not balanced) reciprocity were negatively and positively (respectively) related to employees’ affective organizational commitment and fully mediated the relationship between psychological contract breach and affective organizational commitment. Moreover, affective organizational commitment fully mediated the relationship between generalized and negative reciprocity and employees’ turnover intentions. Implications for theory and practice are discussed.
Resumo:
This paper considers how utilizing a model of job-related affect can be used to explain the processes through which perceived training and development influence employee retention. We applied Russell’s model of core affect to categorize four different forms of work attitude, and positioned these as mediators of the relationship between perceived training and development and intention to stay. Using data from 1,191 employees across seven organizations, multilevel analyses found that job satisfaction, employee engagement, and change-related anxiety were significantly associated with intention to stay, and fully mediated the relationship between perceived training and development and intention to stay. Contrary to our hypotheses, emotional exhaustion was not significantly associated with intention to stay nor acted as a mediator when the other attitudes were included. These findings show the usefulness of Russell’s model of core affect in explaining the link between training and development and employee retention. Moreover, the findings collectively suggest that studies examining employee retention should include a wider range of work attitudes that highlight pleasant forms of affect.