Factorization and reduction methods for optimal control of distributed parameter systems

A Chandrasekhar-type factorization method is applied to the linear-quadratic optimal control problem for distributed parameter systems. An aeroelastic control problem is used as a model example to demonstrate that if computationally efficient algorithms, such as those of Chandrasekhar-type, are combined with the special structure often available to a particular problem, then an abstract approximation theory developed for distributed parameter control theory becomes a viable method of solution. A numerical scheme based on averaging approximations is applied to hereditary control problems. Numerical examples are given

Pair production rates in mildly relativistic, magnetized plasmas

Electron-positron pairs may be produced by either one or two photons in the presence of a strong magnetic field. In magnetized plasmas with temperatures kT approximately sq mc, both of these processes may be important and could be competitive. The rates of one-photon and two-photon pair production by photons with Maxwellian, thermal bremsstrahlung, thermal synchrotron and power law spectra are calculated as a function of temperature or power law index and field strength. This allows a comparison of the two rates and a determination of the conditions under which each process may be a significant source of pairs in astrophysical plasmas. It is found that for photon densities n(gamma) or = 10 to the 25th power/cu cm and magnetic field strengths B or = 10 to the 12th power G, one-photon pair production dominates at kT approximately sq mc for a Maxwellian, at kT approximately 2 sq mc for a thermal bremsstrahlung spectrum, at all temperatures for a thermal synchrotron spectrum, and for power law spectra with indices s approximately 4

Topological entropy and blocking cost for geodesics in riemannian manifolds

For a pair of points $x,y$ in a compact, riemannian manifold $M$ let $n_t(x,y)$ (resp. $s_t(x,y)$) be the number of geodesic segments with length $\leq t$ joining these points (resp. the minimal number of point obstacles needed to block them). We study relationships between the growth rates of $n_t(x,y)$ and $s_t(x,y)$ as $t\to\infty$. We derive lower bounds on $s_t(x,y)$ in terms of the topological entropy $h(M)$ and its fundamental group. This strengthens the results of Burns-Gutkin \cite{BG06} and Lafont-Schmidt \cite{LS}. For instance, by \cite{BG06,LS}, $h(M)>0$ implies that $s$ is unbounded; we show that $s$ grows exponentially, with the rate at least $h(M)/2$.Comment: 13 page

Performance and operational economics estimates for a coal gasification combined-cycle cogeneration powerplant

A performance and operational economics analysis is presented for an integrated-gasifier, combined-cycle (IGCC) system to meet the steam and baseload electrical requirements. The effect of time variations in steam and electrial requirements is included. The amount and timing of electricity purchases from sales to the electric utility are determined. The resulting expenses for purchased electricity and revenues from electricity sales are estimated by using an assumed utility rate structure model. Cogeneration results for a range of potential IGCC cogeneration system sizes are compared with the fuel consumption and costs of natural gas and electricity to meet requirements without cogeneration. The results indicate that an IGCC cogeneration system could save about 10 percent of the total fuel energy presently required to supply steam and electrical requirements without cogeneration. Also for the assumed future fuel and electricity prices, an annual operating cost savings of 21 percent to 26 percent could be achieved with such a cogeneration system. An analysis of the effects of electricity price, fuel price, and system availability indicates that the IGCC cogeneration system has a good potential for economical operation over a wide range in these assumptions

Origin of deformed conglomerate and pseudo deformed conglomerate

Rocks produced by the deformation of conglomeratic sediments strongly resemble pseudodeformed conglomerates in which tectonic disruption of beds, veins and pebbles produce pebblelike bodies. The Goat Island Conglomerate is a tectonic melange containing numerous tectonically formed fragments but is dominantly a metaconglomerate

Young people, sexuality and the age of pornography

Recently interest into the effects of pornography on children and young people’s sexual development has increased leading to an increase in studies in the area, laws being changed and public concern growing. This paper aims to recap these findings including more recent studies carried out in the UK. The literature shows links between viewing pornography and sexually explicit material and young people’s attitudes and behaviours. This suggests that young people’s sexuality is affected by sexual imagery and that this influences children and young people’s sexual attitudes and behaviours. The impact is contingent on the young person’s support network, social learning and other demographic factors, not least gender which has been consistently found to be significant. Recent studies have found changes in sexual practices of young people which are attributed to viewing pornography such as an increase in anal sex and casual attitudes to consent. Links between porn use and sexual coercion have also been found. How and in what ways children and young people are affected by such imagery - and what can be done to reduce the negative impact on young people is debated in the light of the gaps in the literature and the issues with the existing literature. Further need for study is discussed

The momentum distribution of J/psi in B decays

The discrepancy between theory and data in the momentum distribution of slow J/psi in B decays has been several times addressed as a puzzle. Using the most recent results on exclusive B decays into J/psi and heavy kaons or exotic mesons and reconsidering the non-relativistic-QCD calculation of the color octet fragmentation component, we show that an improvement in the comparison between data and theory can be obtained. There is still room for a better fit to data and this may imply that new exotic mesons of the XYZ kind have yet to be discovered.Comment: 4 pages, 2 figures, 2 tables. To appear in Physical Review

“Living with aphasia the best way I can”: a feasibility study exploring solution focused brief therapy for people with aphasia

Objective: Post-stroke aphasia can profoundly affect a person’s social and emotional well-being. This study explored the feasibility of solution focused brief therapy as an accessible intervention, and investigated its impact on participants’ psychosocial well-being. Participants and methods: Small-scale repeated measures feasibility study. Participants received between three and five therapy sessions. They were assessed on psychosocial outcome measures pre and post therapy, and took part in post-therapy in-depth qualitative interviews. Three men and two women with chronic aphasia took part; age range 40s to 70s. Results: Participants found the therapy acceptable and it was possible to adapt the approach so as to be communicatively accessible. Quantitative assessments showed encouraging trends in improved mood: pre-therapy GHQ-12 mean (SD): 4.80 (4.60), median: 6; post therapy mean (SD): 2.00 (2.55), median: 1; and improved communicative participation: pre-therapy CPIB mean (SD): 7.80 (5.76), median: 7; post therapy mean (SD): 12.20 (4.44), median: 14. Measures of social network and connectedness, however, remained stable. Themes emerging from the qualitative analysis included changes to mood, communicative participation, mobility and everyday activities. Conclusions: This small-scale study suggests solution focused brief therapy is a promising approach in helping people with aphasia build positive change in their lives