Low harmonic distortion flash A/D converters incorporating dynamic element matching techniques

New dynamic element matching techniques are shown to reduce the harmonic distortion and improve the spurious-free dynamic range of flash ADCs. Resistor chain mismatch errors are negated by randomly rearranging the resistors each sample by utilizing 5(2{dollar}\sp{b}{dollar}-1) digital switches and b + 1 random control signals for a b-bit flash ADC. The integral and differential nonlinearity of a non-ideal flash ADC are derived for three common resistor chain mismatch errors; namely, geometric mismatches, linear gradient mismatches, and dynamic mismatches. The transfer function of a non-ideal flash ADC is also derived and the converter output is shown to consist of a scaled copy of the input, a DC gain, and conversion noise that is a function of the resistor mismatches. A comprehensive summary of dynamic element matching techniques given in literature is provided. In addition, the DEM network introduced by Galton and Jensen is shown to be equivalent to the generalized-cube network used in parallel processing architectures. An alternative version of this network that uses logic gates is also proposed

Winter bird communities in pine woodland vs. broadleaf forest on Abaco

We assessed the relative abundance of winter resident birds (species that breed in North America but spend the winter in The Bahamas) through 115 point counts conducted during December and January 2007–2012 on Abaco, The Bahamas. We also analyzed structure and composition of the woody vegetation in Abaco’s two widespread terrestrial habitats: Pineland, an open woodland of Pinus caribaea var. bahamensis (Bahamas Pine) that covers most of the island; and Coppice, a broadleaf, relatively diverse forest that covers <10% of Abaco. Winter resident birds were more abundant in Pineland (8.61 individuals/point) than in Coppice (2.28 individuals/point). Setophaga palmarum (Palm Warbler) and S. coronata (Yellow-rumped Warbler) dominated the winter bird communities in Pineland (44.6% and 37.4% of all detected individuals, respectively), with the next three most common species (S. discolor [Prairie Warbler], Dumetella carolinensis [Gray Catbird], and Geothlypis trichas [Common Yellowthroat]) ranging from 6.5 to 2.0%. The winter species composition in Coppice was more even than in Pineland, featuring S. ruticilla [American Redstart] (39.8%), Prairie Warbler (16.2%), Gray Catbird (13.1%), and the next five most common species (S. americana [Northern Parula], Seiurus aurocapillus [Ovenbird], S. caerulescens [Black-throated Blue Warbler], Mnio- tilta varia [Black-and-white Warbler], and S. citrina [Hooded Warbler]) ranging from 7.3 to 3.1%. In Pineland, bird community composition varied with overstory cover and height, understory cover and type, and ground cover. In contrast, patterns of bird community composition in Coppice were not associated strongly with variation in habitat structure or forest composition. This may reflect that Coppice, experiencing frequent hurricane disturbance, has considerable small-scale heterogeneity in the availability of food for winter resident birds. Comparing our data with those from previous surveys of winter birds conducted 5–40 years earlier in the northern Bahamas, we see little evidence of major changes in this bird community

The Lizards of Rarotonga and Mangaia, Cook Island Group, Oceania

Eight species of lizards are reported from the islands of Rarotonga and Mangaia with comments on their distribution, ecology, reproduction, and variation. Particular attention is given to systematic problems in the genus Cryptoblepharus and pattern polymorphism in Emoia cyanura. Emoia trossula, recently described from Fiji, is reported for the first time in the Cook Islands. Historic and zoogeographic evidence suggests that most species of lizards arrived on Rarotonga and Mangaia in Polynesian voyaging canoes within the past 1000 years, although Gehyra mutilata and Hemidactylus garnotii may have arrived by incidental boat or air transport in the past several decades

Normative Primitivism and the Possibility of Practical Thought

Reasons are essentially addressed to agents. Many contemporary efforts to illuminate this feature of reasons effectively reduce them to features of agents, e.g., to rationally-pruned desires, plans, or roles. Such reductive accounts neglect a second feature of reasons, namely, their capacity to transcend agential nature. They also neglect a feature of agents, namely, their orientation to normative entities as entities that transcend—and thus, that can guide and give shape to—agential nature. This dissertation offers a conception of the relation running from reasons to agents that captures both the transcendent character of reasons and the transcended character of agents. I synthesize two strains of thought about reasons. The first captures their formal dependence on agency, which is manifested in each reason’s being essentially a reason for some agent to do or think something. The second captures their substantive independence from agency, which is manifested in the fact that reasons needn’t answer to what agents are like. These two strains of thought can be united in a single conception, but only if the elaboration of the formal features of reasons isn’t taken to license the reduction of reasons to features of agents. In fact, unifying the two in a single conception requires that the relevant agential features be themselves depicted as formally dependent on features of reasons, so that the explanatory landscape for the philosophy of reasons and agents is properly represented in terms of the symmetric relations of a circle, rather than the asymmetric relations of reduction. This refusal to reduce is best framed by primitivism about reasons, i.e., the view that characterizes the idea of reason as primitive. But such a primitivism must nevertheless supply the materials for an account of the practical thought by which agents can receive reasons as addressed to them. I seek to demonstrate how an idea can be primitive while at the same time supplying those materials, and thereby explaining the possibility of practical thought

Normative Primitivism and the Possibility of Practical Thought

Reasons are essentially addressed to agents. Many contemporary efforts to illuminate this feature of reasons effectively reduce them to features of agents, e.g., to rationally-pruned desires, plans, or roles. Such reductive accounts neglect a second feature of reasons, namely, their capacity to transcend agential nature. They also neglect a feature of agents, namely, their orientation to normative entities as entities that transcendand thus, that can guide and give shape toagential nature. This dissertation offers a conception of the relation running from reasons to agents that captures both the transcendent character of reasons and the transcended character of agents. I synthesize two strains of thought about reasons. The first captures their formal dependence on agency, which is manifested in each reasons being essentially a reason for some agent to do or think something. The second captures their substantive independence from agency, which is manifested in the fact that reasons neednt answer to what agents are like. These two strains of thought can be united in a single conception, but only if the elaboration of the formal features of reasons isnt taken to license the reduction of reasons to features of agents. In fact, unifying the two in a single conception requires that the relevant agential features be themselves depicted as formally dependent on features of reasons, so that the explanatory landscape for the philosophy of reasons and agents is properly represented in terms of the symmetric relations of a circle, rather than the asymmetric relations of reduction. This refusal to reduce is best framed by primitivism about reasons, i.e., the view that characterizes the idea of reason as primitive. But such a primitivism must nevertheless supply the materials for an account of the practical thought by which agents can receive reasons as addressed to them. I seek to demonstrate how an idea can be primitive while at the same time supplying those materials, and thereby explaining the possibility of practical thought

Underground mining of aggregates. Main report

This report examines the economic feasibility of underground mining for crushed rock aggregates in the UK, but particularly in the London, South East and East of England regions (the South East area of England). These regions import substantial volumes of crushed rock, primarily from the East Midlands and South West regions, requiring relatively long transport distances to market for this bulk commodity. A key part of the research was to determine whether or not aggregate could be produced and delivered to a local market from an underground aggregates operation at a cost comparable with that for production and transport of the commodity from traditional surface quarries located further afield. In essence the investigation asked – could the reduced transport costs compensate for the higher production costs underground so that underground crushed rock aggregates producers can compete with the established Leicestershire and Somerset surface quarries exporting to the South East? Work Programme The research effort involved establishing and verifying cost models for aggregates production, stone processing (sizing and sorting), haulage of product to market, environmental impact mitigation, health and safety, decommissioning and restoration. Another major element of the work was the re-examination of the BGS exploratory borehole and geophysical databases to identify potential areas of crushed rock aggregates resource at depth in the South East area of England. Land use pressure is typically higher in this area of England than elsewhere so another major part of the research was the identification of potential concurrent uses of land around the surface facilities of underground aggregates mines. The value, development costs for specific developments and determination of yields expected, from these uses were estimated. These were also used to investigate potential economic benefits associated with after uses of remediated surface land above potential underground aggregates mines and also for the new underground space that would be created. Key technical issues such as subsidence within relatively heavily populated areas of the South East area of England were also addressed. Economic Results The discounted cost of aggregate delivered at a discount rate of 10% was the metric used to appraise the options. This is the price of aggregate that leads to a zero net present value of project cash flows realised over the aggregates project life. The results show that the discounted costs of aggregate delivered to a local South East area of England market from an underground mine producing 3.5 million tonnes per annum (MTPA) of crushed rock aggregates, are in the range of £13.03 per tonne to £13.93 per tonne for the top six prospect locations. These are greater than the corresponding cost for a “reference” quarry in Leicestershire producing 3.5 MTPA (£10.95 per tonne), but lower than a “reference” quarry in Leicestershire producing 1.25 MTPA (£16.48 per tonne). These figures indicate that underground crushed rock aggregate mines located within the South East area of England may be able to compete for a share in the overall market by replacing / displacing aggregate imported from the quarries in Leicestershire and Somerset producing around or less than 1.25 MTPA. The surprise in these figures is not really that the more remote surface quarry has a lower discounted cost of aggregate delivered, but that the values for the quarry and underground mine are so close. The capital intensity for the development of underground aggregates mines was found to be higher than that required for surface quarries of comparable scale, by a factor ranging from 1.33 to 1.65 and thus may represent a disincentive for aggregates operators. Carbon Emissions The total carbon emissions of the ‘reference’ 3.5 MTPA quarry in Leicestershire were estimated at 9.28 kg CO2/tonne aggregate delivered and this is to be compared with carbon emissions for the 150 metre deep underground mines serving the local market which were estimated at 9.31 kg CO2/tonne delivered for a Bletchley prospect using an adit to access the sub-surface and 14.25 kg CO2/tonne delivered for a prospect based on the Chitty bore hole using a shaft. Depth of the mine is a key factor in determination of the relative carbon emissions from each of the underground mining operations considered as electricity consumption for ventilation, pumping and winding is proportional to depth. Recommendations The current research generated seven principal recommendations which are discussed in detail in the concluding section of the report. These are: Appraise policy incentives for underground aggregates mining. Conduct an industry-wide consultation on findings from the current research. Obtain public and stakeholder opinion on new uses for underground space. Conduct research to reducing the energy intensity of mine services. Develop a deep level aggregates-specific drilling campaign. Investigate underground aggregates mines developed from existing surface quarries. Investigate underground aggregates as co-products of industrial minerals mining

Earliest Mexican Turkeys (Meleagris gallopavo) in the Maya Region: Implications for Pre-Hispanic Animal Trade and the Timing of Turkey Domestication

Late Preclassic (300 BC–AD 100) turkey remains identified at the archaeological site of El Mirador (Petén, Guatemala) represent the earliest evidence of the Mexican turkey (Meleagris gallopavo) in the ancient Maya world. Archaeological, zooarchaeological, and ancient DNA evidence combine to confirm the identification and context. The natural pre-Hispanic range of the Mexican turkey does not extend south of central Mexico, making the species non-local to the Maya area where another species, the ocellated turkey (Meleagris ocellata), is indigenous. Prior to this discovery, the earliest evidence of M. gallopavo in the Maya area dated to approximately one thousand years later. The El Mirador specimens therefore represent previously unrecorded Preclassic exchange of animals from northern Mesoamerica to the Maya cultural region. As the earliest evidence of M. gallopavo found outside its natural geographic range, the El Mirador turkeys also represent the earliest indirect evidence for Mesoamerican turkey rearing or domestication. The presence of male, female and sub-adult turkeys, and reduced flight morphology further suggests that the El Mirador turkeys were raised in captivity. This supports an argument for the origins of turkey husbandry or at least captive rearing in the Preclassic

Organising a multidisciplinary postgraduate colloquium

The Warwick Postgraduate Colloquium in Computer Science (WPCCS) is an annual event for research students in the Department of Computer Science at the University of Warwick. The aims of the colloquium are to provide: (i) an experience of a conference setting for students, (ii) a place to practise presentation skills, (iii) a place to receive feedback and suggestions on their research, and (iv) an opportunity to learn about research being performed by other attendees. WPCCS has been held annually since 2003, but since 2016 many changes have been made to the event; in particular the introduction of networking aids (such as conference guides and lanyards), a new venue, the introduction of guest speakers and various efforts to encourage attendance. Meanwhile the number of submissions has increased, placing strain on the colloquium’s schedule and budget. In this paper the organising committees from 2016, 2017, and 2018 reflect critically on the experience WPCCS delivers to the attendees. We present an examination of what worked well, what did not work, and what we would like to try in the future, with the aim that these experiences are useful to the organisers of similar events

Measuring magnetic hysteresis curves with polarized soft X‐ray resonant reflectivity

Calculations and measurements of polarization‐dependent soft X‐ray scattering intensity are presented during a magnetic hysteresis cycle. It is confirmed that the dependence of the intensity on the magnetic moment can be linear, quadratic or a combination of both, depending on the polarization of the incident X‐ray beam and the direction of the magnetic moment. With a linearly polarized beam, the scattered intensity will have a purely quadratic dependence on the magnetic moment when the magnetic moment is parallel to the scattering plane. However, with the magnetic moment perpendicular to the scattering plane, there is also a linear component. This means that, when measuring the hysteresis with linear polarization during a hysteresis cycle, the intensity will be an even function of the applied field when the change in the magnetic moment (and field) is confined within the scattering plane but becomes more complicated when the magnetic moment is out of the scattering plane. Furthermore, with circular polarization, the dependence of the scattered intensity on the moment is a combination of linear and quadratic. With the moment parallel to the scattering plane, the linear component changes with the helicity of the incident beam. Surprisingly, in stark contrast to absorption studies, even when the magnetic moment is perpendicular to the scattering plane there is still a dependence on the moment with a linear component. This linear component is completely independent of the helicity of the beam, meaning that the hysteresis loops will not be inverted with helicity