The development and calibration of a generic dynamic absorption chiller model

Although absorption cooling has been available for many years, the technology has typically been viewed as a poorly performing alternative to vapour compression refrigeration. Rising energy prices and the requirement to improve energy efficiency is however driving renewed interest in the technology, particularly within the context of combined cooling, heat and power systems (CCHP) for buildings. In order to understand the performance of absorption cooling, numerous models are available in the literature. However, the complexities involved in the thermodynamics of absorption chillers have so far restricted researchers to creating steady state or dynamic models reliant on data measurements of the internal chiller state, which require difficult-to-obtain, intrusive measurements. The pragmatic, yet fully-dynamic model described in this paper is designed to be easily calibrated using data obtained from the measurements of inflows and outflows to a chiller, without resorting to intrusive measurements. The model comprises a series of linked control volumes featuring both performance maps and lumped mass volumes, which reflect the underlying physical structure of the device. The model was developed for the ESP-r building simulation tool. This paper describes the modelling approach, theory and limitations, along with its calibration and the application of the model to a specific example

Tuning ferromagnetism at interfaces between insulating perovskite oxides

We use density functional theory calculations to show that the LaAlO3|SrTiO3 interface between insulating perovskite oxides is borderline in satisfying the Stoner criterion for itinerant ferromagnetism and explore other oxide combinations with a view to satisfying it more amply. The larger lattice parameter of an LaScO3|BaTiO3 interface is found to be less favorable than the greater interface distortion of LaAlO3|CaTiO3. Compared to LaAlO3|SrTiO3, the latter is predicted to exhibit robust magnetism with a larger saturation moment and a higher Curie temperature. Our results provide support for a "two phase" picture of coexistent superconductivity and ferromagnetism.Comment: 5 pages, 4 figure

Evaluation of a risk assessment system for heritage railway earthworks

There are currently over 100 heritage railways in the UK carrying 6.8 million passengers on 15 million passenger journeys and contributing an estimated £579 million to the UK economy. Many of these lines include significant earthworks, which present a considerable risk to their safe operation. In the last decade there have been major slips at several heritage railways causing major disruption to operations and a serious threat to business continuity. This research describes the application of a risk assessment system based on that used by Network Rail but specifically adapted for heritage railway conditions. Adaptations include significant alterations to the consequence categories used in prioritization of earthwork issues and a simple low-cost method of implementation based on paper forms and Excel spreadsheets. Use of the system on two heritage railways, the Bo’ness and Kinneil Railway and the Strathspey Railway is evaluated by means of discussion with railway engineering staff and civil engineering volunteers. It is concluded that whilst the system represents a realistic and useful approach to management of earthwork assets, the system could not be used by heritage railway volunteer staff without targeted training. Such training, however, would be straightforward to provide, perhaps under the auspices of the Heritage Railway Association

Large potential steps at weakly interacting metal-insulator interfaces

Potential steps exceeding 1 eV are regularly formed at metal|insulator interfaces, even when the interaction between the materials at the interface is weak physisorption. From first-principles calculations on metal|h-BN interfaces we show that these potential steps are only indirectly sensitive to the interface bonding through the dependence of the binding energy curves on the van der Waals interaction. Exchange repulsion forms the main contribution to the interface potential step in the weakly interacting regime, which we show with a simple model based upon a symmetrized product of metal and h-BN wave functions. In the strongly interacting regime, the interface potential step is reduced by chemical bonding

Prediction of thickness limits of ideal polar ultrathin films

Competition between electronic and atomic reconstruction is a constantly recurring theme in transition-metal oxides. We use density functional theory calculations to study this competition for a model system consisting of a thin film of the polar, infinite-layer structure ACuO2 (A=Ca, Sr, Ba) grown on a nonpolar, perovskite SrTiO3 substrate. A transition from the bulk planar structure to a chain-type thin film accompanied by substantial changes to the electronic structure is predicted for a SrCuO2 film fewer than five unit cells thick. An analytical model explains why atomic reconstruction becomes more favorable than electronic reconstruction as the film becomes thinner, and suggests that similar considerations should be valid for other polar films

The TRECVID 2007 BBC rushes summarization evaluation pilot

This paper provides an overview of a pilot evaluation of video summaries using rushes from several BBC dramatic series. It was carried out under the auspices of TRECVID. Twenty-two research teams submitted video summaries of up to 4% duration, of 42 individual rushes video files aimed at compressing out redundant and insignificant material. The output of two baseline systems built on straightforward content reduction techniques was contributed by Carnegie Mellon University as a control. Procedures for developing ground truth lists of important segments from each video were developed at Dublin City University and applied to the BBC video. At NIST each summary was judged by three humans with respect to how much of the ground truth was included, how easy the summary was to understand, and how much repeated material the summary contained. Additional objective measures included: how long it took the system to create the summary, how long it took the assessor to judge it against the ground truth, and what the summary's duration was. Assessor agreement on finding desired segments averaged 78% and results indicate that while it is difficult to exceed the performance of baselines, a few systems did

The Internet and Democratic Debate

Presents findings from a survey conducted in June 2004. Looks at the role of the Internet in providing a wider awareness of political views during the 2004 campaign season

Mapping Australia’s economy: cities as engines of prosperity

This report maps the Australian economy by the location of economic activity, defined as the dollar value of goods and services produced by workers within a particular area. Overview Eighty per cent of the value of all goods and services produced in Australia is generated on just 0.2 per cent of the nation’s land mass – mostly in cities. Today, cities are the engines of economic prosperity. But the concentration of highly productive activity in city centres presents challenges for policymakers. Too many workers live too far away to fulfil our cities’ economic potential. This report maps the Australian economy by the location of economic activity, defined as the dollar value of goods and services produced by workers within a particular area. It finds that economic activity is concentrated most heavily in the central business districts (CBDs) and inner areas of large cities. The CBDs of Sydney and Melbourne – just 7.1 square kilometres in total – generated $118 billion in 2011-12, almost 10 per cent of all economic activity in Australia, and triple the contribution of the entire agriculture sector. The intense economic contribution of CBDs occurs partly because of the concentration of jobs in these areas. But CBD businesses are also much more productive on average than those in other areas. Inner city areas and secondary commercial hubs, such as those around large cities’ airports, also tend to be more productive than other locations. For example, in 2011-12 the Sydney CBD produced$64.1 billion worth of goods and services: about $100 for every hour worked there. Employing only 13 per cent of Sydney’s workforce, this small area generates almost a quarter of the value of the Greater Sydney economy. Parramatta, often said to be Sydney’s second CBD, generated only$68 for each hour worked, and its total of $6.8 billion was about a tenth of the value generated in the CBD. There is a reason intense economic activity is concentrating in CBDs and inner suburbs. Many businesses in these areas provide highly knowledge-intensive and specialised services such as funds management, insurance, design, engineering and international education. These businesses depend on highly skilled workers, and locating in the heart of large cities gives them access to the largest possible pools of them. Proximity to suppliers, customers and partners also helps businesses to work efficiently, to generate opportunities and to come up with new ideas and ways of working. Knowledge-intensive activity is present in all sectors, including manufacturing and mining. Perth’s CBD is home to more than a third of Western Australian mining jobs, including accountants, administrators, geologists and specialist engineers. In the early 20th century one in three workers were employed in primary industry and almost half of the population lived on rural properties or in towns of less than 3,000 people. By 1960 manufacturing had grown to make up almost 30 per cent of GDP and employ one in four Australians, with a big presence in suburban areas. But today the small areas that generate most value are often a very long commute from the fast-growing outer suburbs in which many Australians live. If the prosperity that comes from knowledge-intensive activity is to be widely shared, governments need to enable more people to live closer to these areas, and to improve road and public transport networks so that they better connect employers and workers