Vagueness as Cost Reduction : An Empirical Test

This work was funded in part by an EPSRC Platform Grant awarded to the NLG group at Aberdeen.Publisher PD

Unified formulation of a family of iterative solvers for power systems analysis

This paper illustrates the construction of a new class of iterative solvers for power flow calculations based on the method of Alternating Search Directions. This method is fit to the particular algebraic structure of the power flow problem resulting from the combination of a globally linear set of equations and nonlinear local relations imposed by power conversion devices, such as loads and generators. The choice of the search directions is shown to be crucial for improving the overall robustness of the solver. A noteworthy advantage is that constant search directions yield stationary methods that, in contrast with Newton or Quasi-Newton methods, do not require the evaluation of the Jacobian matrix. Such directions can be elected to enforce the convergence to the high voltage operative solution. The method is explained through an intuitive example illustrating how the proposed generalized formulation is able to include other nonlinear solvers that are classically used for power flow analysis, thus offering a unified view on the topic. Numerical experiments are performed on publicly available benchmarks for large distribution and transmission systems.Peer ReviewedPostprint (author's final draft

Economic model predictive control for optimal operation of combined heat and power systems

© 2019. ElsevierThe use of decentralized Combined Heat and Power (CHP) plants is increasing since the high levels of efficiency they can achieve. Hence, to determine the optimal operation of these systems in the changing energy market, the time-varying price profiles for both electricity as well as the required resources and the energy-market constraints should be considered into the design of the control strategies. To solve these issues and maximize the profit during the operation of the CHP plant, this paper proposes an optimization-based controller, which will be designed according to the Economic Model Predictive Control (EMPC) approach. The proposed controller is designed considering a non-constant time step to get a high sampling frequency for the near instants and a lower resolution for the far instants. Besides, a soft constraint to met the market constraints for the sale of electric power is proposed. The proposed controller is developed based on a real CHP plant installed in the ETA research factory in Darmstadt, Germany. Simulation results show that lower computational time can be achieved if a non-constant step time is implemented while the market constraints are satisfied.Peer ReviewedPostprint (author's final draft

Theory of quantum fluctuations of optical dissipative structures and its application to the squeezing properties of bright cavity solitons

We present a method for the study of quantum fluctuations of dissipative structures forming in nonlinear optical cavities, which we illustrate in the case of a degenerate, type I optical parametric oscillator. The method consists in (i) taking into account explicitly, through a collective variable description, the drift of the dissipative structure caused by the quantum noise, and (ii) expanding the remaining -internal- fluctuations in the biorthonormal basis associated to the linear operator governing the evolution of fluctuations in the linearized Langevin equations. We obtain general expressions for the squeezing and intensity fluctuations spectra. Then we theoretically study the squeezing properties of a special dissipative structure, namely, the bright cavity soliton. After reviewing our previous result that in the linear approximation there is a perfectly squeezed mode irrespectively of the values of the system parameters, we consider squeezing at the bifurcation points, and the squeezing detection with a plane--wave local oscillator field, taking also into account the effect of the detector size on the level of detectable squeezing.Comment: 10 figure

Generalized parametric solutions in Stokes flow

The final publication is available at Springer via https://doi.org/10.1016/j.cma.2017.07.016Design optimization and uncertainty quantification, among other applications of industrial interest, require fast or multiple queries of some parametric model. The Proper Generalized Decomposition (PGD) provides a separable solution, a computational vademecum explicitly dependent on the parameters, efficiently computed with a greedy algorithm combined with an alternated directions scheme and compactly stored. This strategy has been successfully employed in many problems in computational mechanics. The application to problems with saddle point structure raises some difficulties requiring further attention. This article proposes a PGD formulation of the Stokes problem. Various possibilities of the separated forms of the PGD solutions are discussed and analyzed, selecting the more viable option. The efficacy of the proposed methodology is demonstrated in numerical examples for both Stokes and Brinkman models.Peer ReviewedPostprint (author's final draft

The pragmatic competence of Finnish and Japanese learners of English : a comparative study with emphasis on the effect of cultural differences

This thesis studies the pragmatic competence of Finnish and Japanese English learners. The pragmatic competence of the learners in the two countries were compared for the implications the differences might have for teaching of pragmatic competence. In addition, the thesis investigated the effect cultural distance might have on pragmatic competence, as Japan and Finland have different cultural distances to the target language country of Great Britain. The subjects of this study consisted of two groups, a group of 64 first year upper secondary school English learners from Finland and a group of 69 first year high school English learners from Japan. The pragmatic competence of these two groups of learners was assessed with a multiple choice test of pragmatic competence which was adapted from two pre-existing test batteries. The test scores and the answers of the two groups were contrasted with each other in order to establish differences between the two groups of learners. The correlation of the scores in contrast to the countries’ cultural distance from Great Britain was also assessed in order to investigate the effect cultural distance might have on the pragmatic competence. The study found that there were significant differences between the pragmatic competence of Finnish and Japanese learners, with Finnish learners achieving significantly higher scores in the test of pragmatic competence. This was true with both pragmalinguistic and sociopragmatic competence. The study also found that cultural distance correlated negatively with pragmatic competence, meaning that higher cultural distance to the target language country negatively affected pragmatic competence. The results appear to have implications for teaching of pragmatic competence as Japanese students achieved significantly lower scores for pragmatic competence and previous studies have established that classroom instruction can be effective for teaching of pragmatic competence. Future studies could investigate what kind of differences in the curricula or teaching methods between Finland and Japan could have caused these differences. In addition, as cultural distance appears to have a role in the development of pragmatic competence, assessing how large role it has in contrast to other possible explaining factors could be done more accurately in a future study

Improvising Linguistic Style: Social and Affective Bases for Agent Personality

This paper introduces Linguistic Style Improvisation, a theory and set of algorithms for improvisation of spoken utterances by artificial agents, with applications to interactive story and dialogue systems. We argue that linguistic style is a key aspect of character, and show how speech act representations common in AI can provide abstract representations from which computer characters can improvise. We show that the mechanisms proposed introduce the possibility of socially oriented agents, meet the requirements that lifelike characters be believable, and satisfy particular criteria for improvisation proposed by Hayes-Roth.Comment: 10 pages, uses aaai.sty, lingmacros.sty, psfig.st