Mechanism of shot peening enhancement for the fatigue performance of AA7050-T7451

Shot peening is a dynamic cold working process involving the impingement of peening media onto a substrate surface. Shot peening is commonly employed as a surface treatment technique within the aerospace industry during manufacturing, in order to improve fatigue performance of structural components. The compressive residual stress induced during shot peening is understood to result in fatigue crack growth retardation, improving the performance of shot peened components. However, shot peening is a compromise between the benefit of inducing a compressive residual stress and causing detrimental surface damage. Due to the relatively soft nature of AA7050-T7451, shot peening can result in cracking of the constituent particles, the effect of which is recognized as a ‘critically detrimental influence upon the component’s fatigue performance.’ The intention of this thesis is to understand the balance and fundamentals of these competing phenomena, through analysis involving a comparative study throughout the fatigue life cycle of ‘as manufactured’ versus shot peened AA7050-T7451. A series of dog bone samples were manufactured, with a subset undergoing shot peening surface treatment. Microstructural grain characterization and comparison of ‘as manufactured’ and shot peened AA7050-T7451 has been carried out using scanning electron microscope (SEM), electron back scatter diffraction (EBSD), and energy dispersive spectroscopy (EDS) techniques. A residual stress analysis through interrupted fatigue of ‘as manufactured’ and shot peened AA7050-T7451 was completed utilizing a combination of x-ray diffraction (XRD) and nano-indentation. The fatigue life cycle performance of the ‘as manufactured’ versus shot peened material has been evaluated, including qualitative analysis and comparison of crack initiation and propagation in ‘as manufactured’ and shot peened material. Through this experimentation and analysis, this thesis endeavors to answer the question of what is the mechanism for shot peening enhancement for fatigue performance. An objective of this work is to understand how a cracked particle starts to incubate the short crack into the matrix within a residual stress field

Configurable memory systems for embedded many-core processors

The memory system of a modern embedded processor con- sumes a large fraction of total system energy. We explore a range of different configuration options and show that a reconfigurable design can make better use of the resources available to it than any fixed implementation, and provide large improvements in both performance and energy con- sumption. Reconfigurability becomes increasingly useful as resources become more constrained, so is particularly rele- vant in the embedded space. For an optimised architectural configuration, we show that a configurable cache system performs an average of 20% (maximum 70%) better than the best fixed implementation when two programs are competing for the same resources, and reduces cache miss rate by an average of 70% (maximum 90%). We then present a case study of AES encryption and decryption, and find that a custom memory configuration can almost double performance, with further benefits being achieved by specialising the task of each core when parallelising the program

A novel ‘triple drawdown’ method highlights deficiencies in invasive alien crayfish survey and control techniques

Freshwater crayfish can be successful invaders that threaten native biota and aquatic ecosystems in numerous countries worldwide. Nonetheless, the inability of conventional crayfish survey techniques like trapping and handsearching to yield quantitative population data has limited the understanding of crayfish invasion biology and associated ecological impacts. Here, we employed a novel ‘triple drawdown’ (TDD) method to sample invasive populations of signal crayfish Pacifastacus leniusculus in a headwater stream in Northern England. The method was compared with conventional techniques of trapping and handsearching. The TDD method proved to be an effective technique with high capture efficiency, reporting signal crayfish densities from 20.5 to 110.4 animals/m2 at our study sites. These numbers exceed any previous estimates for similar streams. The TDD showed the vast majority of individuals across all sites were juvenile or sub‐adult (<26 mm CL), with only 2.3% of the population large enough (≥35 mm CL) to be caught in standard traps. Synthesis and applications. The triple drawdown (TDD) method demonstrates strong inefficiencies and biases in conventional crayfish survey and management techniques. Trapping is not recommended for representative sampling or control of juvenile dominated populations. TDDs, which can be adapted and modified to operate in multiple habitat types and freshwater systems, generate robust quantitative data on invasive crayfish population demographics in situ. This can advance our understanding of the biology of an important invader of freshwater systems around the world. Obtaining this data prior and post‐intervention is fundamental to evaluate invasive crayfish management, and we recommend the TDD method to assess the effectiveness of future control measures

Entrepreneurship and liminality: the case of self-storage based businesses

Purpose The paper applies the theoretical lens of liminality to a consideration of transitionary entrepreneurial business locations. The study exemplifies such transitionary locations by empirically exploring the particular case of self-storage based businesses: that is, businesses that operate for a significant number of hours each week from self-storage facilities. Methodology The study draws on interviews with both entrepreneurs operating self-storage based businesses and operators of self-storage facilities. The interview data is supported by site visits, businesses’ websites, promotional and marketing materials and press coverage. Findings Consistent with our liminal lens, entrepreneurs view their time operating from self-storage as a transitional phase. They do not suffer the high levels of uncertainty and unsettledness usually associated with liminality. However, they experience anxiety related to perceptions of operating from a business location outside the mainstream. Whilst the entrepreneurs benefit from additional services provided by the self-storage operators, this may be at the expense of extra ‘liminal’ work and anxiety experienced by the storage operators’ staff. Originality/value Our study contributes to the domain of entrepreneurship by firstly highlighting the use of non-traditional locations for entrepreneurship and secondly by beginning to theorise this phenomenon through the lens of liminality. We also make a theoretical contribution to notion of liminality by showing that liminality may manifest as a dualism: simultaneously engendering both feelings of increased certainty and security and feelings of increased anxiety

Invasion of the signal crayfish, 'Pacifastacus leniusculus', in England: implications for the conservation of the white-clawed crayfish, 'Austropotamobius pallipes'

The spread of invasive species is a key driver of UK native biodiversity loss. The UK’s native white-clawed crayfish, Austropotamobius pallipes, is in severe decline. The primary contemporary cause of this decline is the invasive non-native signal crayfish, Pacifastacus leniusculus, and associated ‘crayfish plague’ Aphanomyces astaci. In this thesis, I provide an updated distribution map of crayfish in England. This work shows that A. pallipes continues to significantly decline within England, whilst P. leniusculus continues to spread. Special Areas of Conservation were also analysed in the context of localised threats. At a regional scale, I explored the impacts of P. leniusculus on native ecological communities in headwaters, using both A. pallipes and crayfish-free rivers as controls. At the highest observed Catch-Per-Unit-Effort, populations of P. leniusculus severely depleted both invertebrate abundance and richness. I considered P. leniusculus population density and structure to be paramount in understanding its invasion ecology, but the literature was often based on biased sampling methods or semi-quantitative data. A novel technique, referred to as a ‘triple drawdown’, was developed and tested along a high density invaded river, with the intention of defining an exhaustive method of surveying P. leniusculus. Densities in excess of 110 m-2 crayfish dominated by young-of-year and juvenile cohorts were recorded. The conservation significance of these findings are considered. Finally, the impact of dense P. leniusculus populations was explored, using Gut Contents Analysis (GCA) and Stable Isotope Analysis (SIA). P. leniusculus exhibited high levels of cannibalism in both low and high density sites. Both SIA and GCA showed a diversification to include other invertebrate groups under high density pressure. As a whole, the thesis shows the importance of understanding the fundamental information of distribution, structure and density of P. leniusculus populations, when attempting to manage this highly damaging invasive species, and conserve A. pallipes

Did political parties in Rossendale and Darwen effectively manage their party brand during the 2015 General Election?

Political branding is a comparatively new area of research which is becoming of increasing interest to political parties, practitioners and academics. The ever increasing interest around political brands, highlights the importance of furthering the limited understanding of the subject area. This study, using a multi-method qualitative research methodology, determines whether political parties in the marginal constituency of Rossendale and Darwen effectively managed their overall party brand during the 2015 General Election. This research furthers the understanding of political brands and the core elements within it, whilst trying to determine which element, if any, has the greatest influence on voters perceptions of the overall party brand. The aims, objectives and research questions have been answered by a critical review of the academic literature on the topic and undertaking primary qualitative research; in the form of focus groups with Rossendale and Darwen constituents; and interviews with representatives from the main three political parties which stood for election in Rossendale and Darwen in 2015. The conclusions which have been developed evaluate whether or not the three main political parties, the Labour Party, the Conservative Party and the United Kingdom Independence Party effectively managed their party brand during the election and determines the influence each element of the political offer has on influencing the overall party brand. The research established that the Conservative Party was the only political party in Rossendale and Darwen that effectively managed their overall party brand during the 2015 General Election. Participants were aware of, understood and positively perceived Conservative policies and the overall party brand which portrayed economic competence and steadfast leadership. The Conservative Party leader, David Cameron, was a crucial element of the party's brand and was integral to the management of the overall image and electorate’s perception of the party. The research concludes that in order to effectively manage the overall party brand, a political party must have a strong political product offering. To be successful, the political offer requires clearly defined and relevant policies; a well positioned and differentiated party brand that the electorate is familiar with and understands; and, finally, the party must have a strong and steadfast leader that posses prime ministerial attributes and can effectively communicate and engage with voters. The research has concluded that of the three political offer elements, the leader is the most important and has the greatest influence on voters’ perception of the overall party brand. The leader is essential in ensuring that the electorate is aware of, understands and is engaged with the party’s candidates, leadership, policies and ideology, particularly during an election campaign

Characterizing Bighorn Sheep Foraging Sites Using the Modified Robel Pole in the Southern Black Hills, South Dakota

Evaluating foraging behavior of bighorn sheep (Ovis canadensis) and filling information gaps for their habitat requirements is important for population level management in the southern Black Hills of South Dakota. Our objectives were to: (1) evaluate the overall summer foraging area post lambing use during July and August for standing herbage with the modified Robel pole (1.27 cm bands) with visual obstruction readings (VOR) related to clipped herbage at ground level; (2) calibrate the Robel pole visual obstruction (bands) with clipped vegetation; and (3) develop guidelines for monitoring the landscape of the bighorn sheep foraging areas. The study area is located in a ponderosa pine (Pinus ponderosa ) savanna with few shrubs and dominated with native grasses. Each transect had 10 visual obstruction (bands) stations spaced 10 meters apart with 4 visual obstruction readings at each station. At 4 stations, total vegetation was clipped at ground level within a 0.25-m2  circular hoop. Clipped standing herbage ranged from 418 kg/ha to 3731 kg/ha with a mean of 1519 kg/ha. VOR measurements ranged from 0.2 cm to 14.9 cm with a 3.9 cm mean. Calibration of the modified Roble pole (visual obstruction of bands) with transect means using linear regression reliability predicted average clipped standing herbage (dry weights) within the bighorn sheep foraging area. The relationship was significant (R2  = 0.65; F1, 27  = 50.75, P  &lt; 0.01). Cluster analysis (ISODATA) applied to the pole readings (VOR) and herbage resulted in 3 categories: short, intermediate and tall. We recommend 14 Robel pole transects (100 m in length) for VOR measurements within key foraging areas for future monitoring of herbaceous biomass for bighorn sheep. Foraging sites were in areas with little overstory tree canopy, close to rocky escape terrain, and where abundant grasses and forbs had little woody debris. The modified Robel pole provides a simple, reliable and cost effective alternative to clipping vegetation and obtaining dry weights