Organic farm incomes in England and Wales 2010/11 (OF 0373)

This report presents results of research on the financial performance of organic farms in the 2010/11 financial year (with 2009/10 data for reference. Carried out for the Department for Environment, Food and Rural Affairs (Defra), this research continues project OF0373. An analysis of the FBS/Defra Data Archive for 2010/11 found a total of 250 businesses with some organic land. To ensure the analysis undertakes a reasonable comparison of organic and conventional farms, the organic sample comprises holdings with at least 70% fully organic land (>=70% of UAA ha). Farms identified as “in-conversion” or those with less than 70% fully organic certified land were excluded from the analysis, providing a sample of 217 organic holdings. In total, data from 212 organic farms were suitable for inclusion in the analysis, as it was not possible to identify comparable conventional businesses for four organic farms, and one organic specialist pig farm was also not utilised (due to minimum sample size restrictions). The data was analysed as two samples; a full sample and an identical sample. The full sample analysis utilised data from all 212 organic farms and provides the best comparison of organic and comparable conventional farm income data in 2010/11, (2009/10 data is only provided for reference). The identical sample identifies year to year changes within systems, though the sample sizes are smaller as not all farms will be part of the FBS dataset for two years

Impact of residential energy system sizing and control over heat pump’s system cost and reliability

Using a simulation-based approach, this work analyses the impact that different energy unit sizes and control methodologies will have over the capital and running costs of an air source heat pump (ASHP) system to be installed in a refurbished dwelling. A total of 9 different heating configuration options were investigated and the cumulative cash flow over a period of 10 years (including initial investment) was utilized to compare the systems from a customer perspective. Additionally, in selected cases, the cycling of the heat pump was calculated in order to estimate the life-span of the device. The building and heat pump systems were simulated using TRNSYS energy system models. The results revealed the sensitivity of the system’s costs and life-span to its operating characteristics. For example, operating the system as a direct gas boiler replacement resulted in capital costs above £10,000 and the unit's life span reduced by half in comparison to more favourable operational strategies. The results highlight the fact that the successful technical and financial performance of heat pumps within the UK’s residential market will depend of designers, installers and end-users’ awareness regarding optimal operational strategies for this technology

Shear-induced fragmentation of Laponite suspensions

Simultaneous rheological and velocity profile measurements are performed in a smooth Couette geometry on Laponite suspensions seeded with glass microspheres and undergoing the shear-induced solid-to-fluid (or yielding) transition. Under these slippery boundary conditions, a rich temporal behaviour is uncovered, in which shear localization is observed at short times, that rapidly gives way to a highly heterogeneous flow characterized by intermittent switching from plug-like flow to linear velocity profiles. Such a temporal behaviour is linked to the fragmentation of the initially solid sample into blocks separated by fluidized regions. These solid pieces get progressively eroded over time scales ranging from a few minutes to several hours depending on the applied shear rate $\dot{\gamma}$. The steady-state is characterized by a homogeneous flow with almost negligible wall slip. The characteristic time scale for erosion is shown to diverge below some critical shear rate $\dot{\gamma}^\star$ and to scale as $(\dot{\gamma}-\dot{\gamma}^\star)^{-n}$ with $n\simeq 2$ above $\dot{\gamma}^\star$. A tentative model for erosion is discussed together with open questions raised by the present results.Comment: 19 pages, 13 figures, submitted to Soft Matte

Markov games with frequent actions and incomplete information

We study a two-player, zero-sum, stochastic game with incomplete information on one side in which the players are allowed to play more and more frequently. The informed player observes the realization of a Markov chain on which the payoffs depend, while the non-informed player only observes his opponent's actions. We show the existence of a limit value as the time span between two consecutive stages vanishes; this value is characterized through an auxiliary optimization problem and as the solution of an Hamilton-Jacobi equation

Expressing social attitudes in virtual agents for social training games

The use of virtual agents in social coaching has increased rapidly in the last decade. In order to train the user in different situations than can occur in real life, the virtual agent should be able to express different social attitudes. In this paper, we propose a model of social attitudes that enables a virtual agent to reason on the appropriate social attitude to express during the interaction with a user given the course of the interaction, but also the emotions, mood and personality of the agent. Moreover, the model enables the virtual agent to display its social attitude through its non-verbal behaviour. The proposed model has been developed in the context of job interview simulation. The methodology used to develop such a model combined a theoretical and an empirical approach. Indeed, the model is based both on the literature in Human and Social Sciences on social attitudes but also on the analysis of an audiovisual corpus of job interviews and on post-hoc interviews with the recruiters on their expressed attitudes during the job interview

Dependence of DNA persistence length on ionic strength of solutions with monovalent and divalent salts: a joint theory-experiment study

Using high-throughput Tethered Particle Motion single molecule experiments, the double-stranded DNA persistence length, $L_p$, is measured in solutions with Na$^+$ and Mg$^{2+}$ ions of various ionic strengths, $I$. Several theoretical equations for $L_p(I)$ are fitted to the experimental data, but no decisive theory is found which fits all the $L_p$ values for the two ion valencies. Properly extracted from the particle trajectory using simulations, $L_p$ varies from 30~nm to 55~nm, and is compared to previous experimental results. For the Na$^+$ only case, $L_p$ is an increasing concave function of $I^{-1}$, well fitted by Manning's electrostatic stretching approach, but not by classical Odjik-Skolnick-Fixman theories with or without counter-ion condensation. With added Mg$^{2+}$ ions, $L_p$ shows a marked decrease at low $I$, interpreted as an ion-ion correlation effect, with an almost linear law in $I^{-1}$, fitted by a proposed variational approach