Cosmic Chemical Evolution

Numerical simulations of standard cosmological scenarios have now reached the degree of sophistication required to provide tentative answers to the fundamental question: Where and when were the heavy elements formed? Averaging globally, these simulations give a metallicity that increases from 1% of the solar value at $z=3$ to 20% at present. This conclusion is, in fact, misleading, as it masks the very strong dependency of metallicity on local density. At every epoch higher density regions have much higher metallicity than lower density regions. Moreover, the highest density regions quickly approach near solar metallicity and then saturate, while more typical regions slowly catch up. These results are much more consistent with observational data than the simpler picture (adopted by many) of gradual, quasi-uniform increase of metallicity with time.Comment: ApJ(Letters) in press, 15 latex pages and 4 figure

The Linear Model under Mixed Gaussian Inputs: Designing the Transfer Matrix

Suppose a linear model y = Hx + n, where inputs x, n are independent Gaussian mixtures. The problem is to design the transfer matrix H so as to minimize the mean square error (MSE) when estimating x from y. This problem has important applications, but faces at least three hurdles. Firstly, even for a fixed H, the minimum MSE (MMSE) has no analytical form. Secondly, the MMSE is generally not convex in H. Thirdly, derivatives of the MMSE w.r.t. H are hard to obtain. This paper casts the problem as a stochastic program and invokes gradient methods. The study is motivated by two applications in signal processing. One concerns the choice of error-reducing precoders; the other deals with selection of pilot matrices for channel estimation. In either setting, our numerical results indicate improved estimation accuracy - markedly better than those obtained by optimal design based on standard linear estimators. Some implications of the non-convexities of the MMSE are noteworthy, yet, to our knowledge, not well known. For example, there are cases in which more pilot power is detrimental for channel estimation. This paper explains why

Adiabatic Gate Teleportation

The difficulty in producing precisely timed and controlled quantum gates is a significant source of error in many physical implementations of quantum computers. Here we introduce a simple universal primitive, adiabatic gate teleportation, which is robust to timing errors and many control errors and maintains a constant energy gap throughout the computation above a degenerate ground state space. Notably this construction allows for geometric robustness based upon the control of two independent qubit interactions. Further, our piecewise adiabatic evolution easily relates to the quantum circuit model, enabling the use of standard methods from fault-tolerance theory for establishing thresholds.Comment: 4 pages, 1 figure, with additional 3 pages and 2 figures in an appendix. v2 Refs added. Video abstract available at http://www.quantiki.org/video_abstracts/0905090

Matching model of flow table for networked big data

Networking for big data has to be intelligent because it will adjust data transmission requirements adaptively during data splitting and merging. Software-defined networking (SDN) provides a workable and practical paradigm for designing more efficient and flexible networks. Matching strategy in the flow table of SDN switches is most crucial. In this paper, we use a classification approach to analyze the structure of packets based on the tuple-space lookup mechanism, and propose a matching model of the flow table in SDN switches by classifying packets based on a set of fields, which is called an F-OpenFlow. The experiment results show that the proposed F-OpenFlow effectively improves the utilization rate and matching efficiency of the flow table in SDN switches for networked big data.Comment: 14 pages, 6 figures, 2 table

‘Multi-directional management’: Exploring the challenges of performance in the World Class Programme environment

Driven by the ever-increasing intensity of Olympic competition and the ‘no compromise – no stone unturned’ requirements frequently addressed by HM Government and its main agency, UK Sport, a change in culture across Olympic team landscapes is a common occurrence. With a focus on process, this paper presents reflections from eight current or recently serving UK Olympic sport Performance Directors on their experiences of creating and disseminating their vision for their sport, a vital initial activity of the change initiative. To facilitate a broad overview of this construct, reflections are structured around the vision’s characteristics and foundations, how it is delivered to key stakeholder groups, how it is influenced by these groups, the qualities required to ensure its longevity and its limitations. Emerging from these perceptions, the creation and maintenance of a shared team vision was portrayed as a highly dynamic task requiring the active management of a number of key internal and external stakeholders. Furthermore, the application of ‘dark’ traits and context-specific expertise were considered critical attributes for the activity’s success. Finally, recent calls for research to elucidate the wider culture optimisation process are reinforced

Recovering a Classically Oral Homiletic

Historically, the preaching of the word of God has been a synthesis of both oral and written orientations with text providing both the source and the preservation of the sermon, and orality fueling its expression. Expression preceded documentation. Scripture displays this dual nature in its revelation, expression and transmission. But with the technologizing of the word in typographic literacy, sermons became increasingly conditioned by the literate sensorium and lost many of their oral psychodynamics. Character, wisdom, dialogue, memory, responsiveness, and flexibility were exchanged for private preparation, literate structuring, and literary delivery. Sermons became disembodied, existing more reliably in externalized text. Walter Ong provides the framework for the reappraisal of communicative history by strategically forgetting the pervasive influence of technology. Recovering the older resources of orality, Ong restores a sense of balance to the oral/literate continuum by returning to the primarily oral orientations of the Greco-Roman world of classic rhetoric, and rehabilitates rhetoric with theological and homiletic implications. Quintilian\u27s infinitely flexible oratory represents the richness of the communicative environment during the infancy of the church. His emphasis on depth of understanding as a prerequisite for public speaking grounds the speaker in resources beyond the pragmatics of the specific situation or topic, and can be profitably applied to contemporary homiletic praxis. Quintilian\u27s understanding of oral composition, memory, roadmapping, and kairos is applicable to the kind of preparation and delivery required by an intentional move toward an orally-conditioned homiletic

Multi-Use Facilities - Repurposing Facilities Infrastructure to Support the Multi-customer Environment

Since the early 90’s the space launch business has undergone significant change in customers, composition, capacity, and key players. These changes have a resultant effect upon the spaceport industry. Some spaceports, in their current state, may not survive the probable future market and business environment. To stay in the game, spaceports are reexamining their target launch vehicles, services, and operations philosophy. One of the strategies being developed to accommodate current and future changes is to repurpose facilities to support multiple customers. The new vision is that multiple commercial, as well as government entities, having multiple spacecraft and launch vehicle configurations will all operate within or upon one multi-purpose facility – including launch pads. One of the challenges is to develop capability for the “first to market” vehicles without increasing price or risk to future users. This presentation will provide the considerations involved in developing facility infrastructure to support the multi-customer environment

Market Impact in Trader-Agents:Adding Multi-Level Order-Flow Imbalance-Sensitivity to Automated Trading Systems

Financial markets populated by human traders often exhibit "market impact", where the traders' quote-prices move in the direction of anticipated change, before any transaction has taken place, as an immediate reaction to the arrival of a large (i.e., "block") buy or sell order in the market: e.g., traders in the market know that a block buy order will push the price up, and so they immediately adjust their quote-prices upwards. Most major financial markets now involve many "robot traders", autonomous adaptive software agents, rather than humans. This paper explores how to give such trader-agents a reliable anticipatory sensitivity to block orders, such that markets populated entirely by robot traders also show market-impact effects. In a 2019 publication Church & Cliff presented initial results from a simple deterministic robot trader, ISHV, which exhibits this market impact effect via monitoring a metric of imbalance between supply and demand in the market. The novel contributions of our paper are: (a) we critique the methods used by Church & Cliff, revealing them to be weak, and argue that a more robust measure of imbalance is required; (b) we argue for the use of multi-level order-flow imbalance (MLOFI: Xu et al., 2019) as a better basis for imbalance-sensitive robot trader-agents; and (c) we demonstrate the use of the more robust MLOFI measure in extending ISHV, and also the well-known AA and ZIP trading-agent algorithms (which have both been previously shown to consistently outperform human traders). We demonstrate that the new imbalance-sensitive trader-agents introduced here do exhibit market impact effects, and hence are better-suited to operating in markets where impact is a factor of concern or interest, but do not suffer the weaknesses of the methods used by Church & Cliff. The source-code for our work reported here is freely available on GitHub.Comment: To be presented at the 13th International Conference on Agents and Artificial Intelligence (ICAART2021), Vienna, 4th--6th February 2021. 15 pages; 9 figure