Numerical verification of equilibrium thermodynamic computations in nuclear fuel performance codes

There is an increasing desire to integrate thermodynamic computations directly into multi-physics nuclear fuel performance and safety codes. These computations provide, among other matters, boundary conditions in heat and mass transport modules in predicting fuel behaviour. Precision must be maintained in computations involving fission and activation products with very low concentrations, which may nonetheless have significant radiological consequences. Also, there is the concern about the propagation of numerical errors in multi-physics codes. A method to numerically verify equilibrium thermodynamic computations is therefore necessary to satisfy rigorous quality assurance standards of the nuclear industry without significantly impeding computational performance. A technique is presented that can be applied to systems of any number of phases and system components. The technique is reliable and comprehensive in ensuring that all conceivable equilibrium constants have been satisfied without having to formulate each one of a potentially very large number.     

Response efficacy: The key to minimizing rejection and maximizing acceptance of emotion-based anti-speeding messages

This study sought to improve understanding of the persuasive process of emotion-based appeals not only in relation to negative, fear-based appeals but also for appeals based upon positive emotions. In particular, the study investigated whether response efficacy, as a cognitive construct, mediated outcome measures of message effectiveness in terms of both acceptance and rejection of negative and positive emotion-based messages. Licensed drivers (N = 406) participated via the completion of an on-line survey. Within the survey, participants received either a negative (fear-based) appeal or one of the two possible positive appeals (pride or humor-based). Overall, the study's findings confirmed the importance of emotional and cognitive components of persuasive health messages and identified response efficacy as a key cognitive construct influencing the effectiveness of not only fear-based messages but also positive emotion-based messages. Interestingly, however, the results suggested that response efficacy's influence on message effectiveness may differ for positive and negative emotion-based appeals such that significant indirect (and mediational) effects were found with both acceptance and rejection of the positive appeals yet only with rejection of the fear-based appeal. As such, the study's findings provide an important extension to extant literature and may inform future advertising message design.     

Field Measurements of Mean Velocity Characteristics of a Large-Diameter Swirling Jet

Full-scale field acoustic Doppler velocimeter measurements of the radial, axial, and tangential flow components were undertaken in a large-diameter turbulent swirling jet generated by a raft-mounted axial flow-mixing propeller discharging through a draft tube during isothermal and stratified conditions. The results were compared with classical jet theory and showed significant differences in the zone of flow establishment though similar behavior in the zone where established flow was found. It was concluded that the efflux from the axial flow-mixing propeller could not be described adequately by conventional jet theory due to the jet size and swirling characteristics.     

Silicon Nitride Rolling Bearings for Extreme Operating Conditions

The high hardness and excellent high-temperature performance of ceramics are attractive for critical rolling-bearing applications, such as in high-thermal-efficiency engines. In addition, the lower density of ceramics permits lower centrifugal loads, less skidding at high speeds, and, consequently, results in longer bearing component life than conventional bearing steels or alternative super-alloys or cermets. Silicon nitride has the lowest friction and elastic modulus of the available ceramics, which reduce bearing contact stresses. This paper reviews the merits and demerits of silicon nitride as a bearing material, its processing, and different mechanisms for solid-lubricant replenishment in severe environments. Test data and application design guidelines accumulated to dale are also provided.     

Replicating the cross-sectional distribution of house-dust mite allergen found in carpet

With a view to producing carpets that could be used to determine the ease of particulate aerosolisation during domestic activity, we measured the cross-sectional distribution of dust-mite allergen, Der p 1, produced using American Society for Testing and Materials method (ASTM F608–89) for embedding house dust in carpets with that produced by several alternative protocols. Allergen concentrations produced at different levels within the pile using the different techniques were also compared with those in carpets from actual houses – in which the majority of allergen is typically found towards the base of the pile. To obtain profiles of allergen, horizontal sections, 2-mm thick, were taken from new carpets after they had been seeded with dust and embedded using one of four following techniques: (1) dragging a fixed roller across the surface of the carpet four times, (2) using the same roller but following it up with 200 revolutions in a hexapod wear simulator, (3) dragging the fixed roller across the carpet surface 30 times (the ASTM method), and (4) 2 minutes under a commercial plate compactor. Fibre from each 2-mm-thick section was collected and the Der p 1 content determined using enzyme linked immunosorbent assay and results expressed as ng Der p 1 per area in each section. Embedding with a fixed roller alone was not found to be particularly effective, resulting in roughly equal amounts of dust being apportioned within each pile layer, irrespective of the number of embedding passes used. In contrast, a distribution biased towards the base of the pile was found after roller-embedding/hexapod wear, although still to a lesser extent than has been observed in used carpets. Plate compaction gave a similar allergen distribution profile to combined roller/hexapod treatment but was considerably easier to perform. Thus, both techniques offer promise for researchers seeking to replicate the cross-sectional distribution of dust mite allergen found in carpets after actual use (and conceivably other particulate pollutants also).     

Canada’s program on nuclear hydrogen production and the thermochemical Cu–Cl cycle

This paper presents an overview of the status of Canada’s program on nuclear hydrogen production and the thermochemical copper–chlorine (Cu–Cl) cycle. Enabling technologies for the Cu–Cl cycle are being developed by a Canadian consortium, as part of the Generation IV International Forum (GIF) for hydrogen production with the next generation of nuclear reactors. Particular emphasis in this paper is given to hydrogen production with Canada’s Super-Critical Water Reactor, SCWR. Recent advances towards an integrated lab-scale Cu–Cl cycle are discussed, including experimentation, modeling, simulation, advanced materials, thermochemistry, safety, reliability and economics. In addition, electrolysis during off-peak hours, and the processes of integrating hydrogen plants with Canada’s nuclear plants are presented.     

Resource allocation in decentralised computational systems: an evolutionary market-based approach

We present a novel market-based method, inspired by retail markets, for resource allocation in fully decentralised systems where agents are self-interested. Our market mechanism requires no coordinating node or complex negotiation. The stability of outcome allocations, those at equilibrium, is analysed and compared for three buyer behaviour models. In order to capture the interaction between self-interested agents, we propose the use of competitive coevolution. Our approach is both highly scalable and may be tuned to achieve specified outcome resource allocations. We demonstrate the behaviour of our approach in simulation, where evolutionary market agents act on behalf of service providing nodes to adaptively price their resources over time, in response to market conditions. We show that this leads the system to the predicted outcome resource allocation. Furthermore, the system remains stable in the presence of small changes in price, when buyers’ decision functions degrade gracefully.     

The Complexity of Public Attitudes Toward Compact Development

Problem: The future of compact development depends in part on understanding and shaping the public's attitudes toward it. Previous studies have suggested life cycle, socioeconomic, attitudinal, and ideological dimensions to preferences regarding development patterns, but rarely have all of these factors been examined systematically across a broad, generalizable sample of respondents.

Purpose: To examine public attitudes toward compact development, we asked survey respondents to weigh four important tradeoffs between compact and sprawling growth. We assess the relative influence of a variety of individual characteristics on these attitudes.

Methods: We use results from two large-scale, randomized telephone surveys, one conducted in California in 2002 and the other in four other southwestern states in 2007. Using logistic regression, we assess which personal characteristics are associated with stated preferences regarding compact development, and illustrate their degree of influence.

Results and conclusions: Support for the compact development alternatives is significant, in some cases exceeding support for traditional, decentralized suburban patterns. However, question wording appears to matter considerably, and individuals’ beliefs about different facets of compact development are often inconsistent. Although race, income, age, and the presence of children in the household are strongly associated with some views on the four tradeoffs, only political ideology is consistently associated with opposition to compact development.

Takeaway for practice: The significant support evident for compact development may not translate into actual housing choices unless local governments and lenders do more to support the production of such housing and neighborhood environments. If, as our results suggest, a major constituency for transit-oriented and mixed-use projects is low income residents, renters, and minorities, then well crafted urban infill projects that take into account the needs of these groups will help fulfill the potential of smart growth. Advocates might also frame compact development to appeal more to political conservatives.

Research support: The 2002 survey was conducted by the Public Policy Institute of California, with financial support from the William and Flora Hewlett Foundation, James Irvine Foundation, and David and Lucille Packard Foundation. The 2007 survey was conducted and supported by the Institute for Social Science Research at Arizona State University. All views expressed are solely those of the authors, not these organizations.     

Design Criteria for Externally Pressurized Gas Bearings for Operation at High Temperatures and High Speeds

The paper describes an experimental program using externally pressurized gas bearings whose objective was to gain design information which would be applicable to operation at high speeds and high temperature. The objective was to maintain flow rates to some acceptable minimum while at the same time attaining requirements of load capacity, temperature, and stable operating conditions. The paper describes work that has been done on a variety of configurations in order to establish some nondimensional stability map. The bulk of the variations were observed at low temperatures as a function of nondimensional parameters which took into account temperature dependent variables. These results were later checked to temperatures of 1200 F and speeds to 60,000 rpm. In order to obtain results with regard to the parameters which were not influenced by certain geometry changes, care was taken to insure that isothermal conditions existed. Later work will be necessary to interject the variable of possible temperature gradients which will result in distortions and geometrical changes.