Mathematical modelling and optimal multivariable control of chemical processes

This work reports the developnent of a mathenatical model and distributed, multi variable computer-control for a pilot plant double-effect climbing-film evaporator. A distributed-parameter model of the plant has been developed and the time-domain model transformed into the Laplace domain. The model has been further transformed into an integral domain conforming to an algebraic ring of polynomials, to eliminate the transcendental terms which arise in the Laplace domain due to the distributed nature of the plant model. This has made possible the application of linear control theories to a set of linear-partial differential equations. The models obtained have well tracked the experimental results of the plant. A distributed-computer network has been interfaced with the plant to implement digital controllers in a hierarchical structure. A modern rnultivariable Wiener-Hopf controller has been applled to the plant model. The application has revealed a limitation condition that the plant matrix should be positive-definite along the infinite frequency axis. A new multi variable control theory has emerged fram this study, which avoids the above limitation. The controller has the structure of the modern Wiener-Hopf controller, but with a unique feature enabling a designer to specify the closed-loop poles in advance and to shape the sensitivity matrix as required. In this way, the method treats directly the interaction problems found in the chemical processes with good tracking and regulation performances. Though the ability of the analytical design methods to determine once and for all whether a given set of specifications can be met is one of its chief advantages over the conventional trial-and-error design procedures. However, one disadvantage that offsets to some degree the enormous advantages is the relatively complicated algebra that must be employed in working out all but the simplest problem. Mathematical algorithms and computer software have been developed to treat some of the mathematical operations defined over the integral domain, such as matrix fraction description, spectral factorization, the Bezout identity, and the general manipulation of polynomial matrices. Hence, the design problems of Wiener-Hopf type of controllers and other similar algebraic design methods can be easily solved.

On the transmission properties of synapses made between granule cells and cerebellar Purkinje cells

In the cerebellar cortex, forms of both long-term depression (LTD) and long-term potentiation (LTP) can be observed at parallel fibre (PF) - Purkinje cell (PC) synapses. A presynaptic variant of cerebellar LTP can be evoked in PCs by raised frequency stimulation (RFS) of parallel fibre at 4-16Hz for 15s. This form of LTP is dependent on protein kinase A (PKA) and nitric oxide (NO), and can spread to distant synapses. Application of an extracellular NO scavenger, cPTIO, was found to prevent the spread of LTP to distant PF synapses in rat cerebellar slices. G-substrate may be an important mediator of the NO-dependent pathway for LTD. 8-16Hz RFS of PFs without a high concentration of calcium chelator in the postsynaptic cell evokes LTD. In cerebellar slices from wild-type and transgenic, G-substrate knockout mice, 8Hz RFS was applied to PFs, with a low concentration of postsynaptic calcium chelator. In PCs from wild-type mice, LTD predominated, whereas in those from transgenic mice LTP predominated. The ascending axon (AA) segment of the granule cell axon forms synapses with PCs as well as the PF segment. PPF and fluctuation analysis of EPSCs in rat PCs confirmed that the release sites of AA synapses have a greater probability of transmitter release than PF synapses. Furthermore, AA release sites have greater mean quantal amplitude than PF synapses, which is not due to a different type of postsynaptic receptor. AA synapses were found to have limited capacity to undergo the presynaptic variant of LTP, and were potentiated less than PF synapses in the presence of the PKA activator, forskolin. AA synapses also did not undergo the postsynaptic form of LTP, nor LTD induced by conjunctive stimulation of climbing fibre and PF.

Shade promotes thorn development in a tropical liana, Artabotrys hexapatalus (Annonaceae)

The liana Artabotrys hexapetalus (L.f.) Bhand., which is widely planted in the Tropics and native to African rain forests, produced new reiterations (new leader shoots) normally and after damage induced by Hurricane Andrew (August 24, 1992). In each new orthotropic shoot, there is a gradient in lateral branch structures from basal thorns, to vegetative leafy branches, to distal leafy flowering branches. We noted that reiterations developing in shade had more thorns than similar reiterations developing in full sun. Tents with clear (66% photosynthetically active radiation [PAR]) and shaded plastic film (12%–14% PAR) were placed over nodes when the axillary buds began to expand to produce reiteration shoots. After 2 mo of growth inside the tents and in the open, the types of lateral outgrowths (thorn vs. branch) were recorded. Shoots in spectrally neutral shade (red to far red of full sun) and spectrally altered shade (red to far red of canopy shade) produced significantly more thorns at the lower nodes of the shoots as compared to those in full sun. Shoots in control clear plastic tents were the same as those in full sun. We conclude that the fate of lateral bud development is controlled by irradiance (light level) but not by light quality. Increased thorn production in shade could be advantageous to plants growing in the deep shade of rain forests. Thorns in the self-shaded regions of the plant, and well below the forest canopy, could aid in protection from herbivory and in climbing by acting as hooks.

Rigid and non-rigid point-based medical image registration

The primary goal of this dissertation is to develop point-based rigid and non-rigid image registration methods that have better accuracy than existing methods. We first present point-based PoIRe, which provides the framework for point-based global rigid registrations. It allows a choice of different search strategies including (a) branch-and-bound, (b) probabilistic hill-climbing, and (c) a novel hybrid method that takes advantage of the best characteristics of the other two methods. We use a robust similarity measure that is insensitive to noise, which is often introduced during feature extraction. We show the robustness of PoIRe using it to register images obtained with an electronic portal imaging device (EPID), which have large amounts of scatter and low contrast. To evaluate PoIRe we used (a) simulated images and (b) images with fiducial markers; PoIRe was extensively tested with 2D EPID images and images generated by 3D Computer Tomography (CT) and Magnetic Resonance (MR) images. PoIRe was also evaluated using benchmark data sets from the blind retrospective evaluation project (RIRE). We show that PoIRe is better than existing methods such as Iterative Closest Point (ICP) and methods based on mutual information. We also present a novel point-based local non-rigid shape registration algorithm. We extend the robust similarity measure used in PoIRe to non-rigid registrations adapting it to a free form deformation (FFD) model and making it robust to local minima, which is a drawback common to existing non-rigid point-based methods. For non-rigid registrations we show that it performs better than existing methods and that is less sensitive to starting conditions. We test our non-rigid registration method using available benchmark data sets for shape registration. Finally, we also explore the extraction of features invariant to changes in perspective and illumination, and explore how they can help improve the accuracy of multi-modal registration. For multimodal registration of EPID-DRR images we present a method based on a local descriptor defined by a vector of complex responses to a circular Gabor filter.

A conceptual ecological model to facilitate understanding the role of invasive species in large-scale ecosystem restoration

We developed a conceptual ecological model (CEM) for invasive species to help understand the role invasive exotics have in ecosystem ecology and their impacts on restoration activities. Our model, which can be applied to any invasive species, grew from the eco-regional conceptual models developed for Everglades restoration. These models identify ecological drivers, stressors, effects and attributes; we integrated the unique aspects of exotic species invasions and effects into this conceptual hierarchy. We used the model to help identify important aspects of invasion in the development of an invasive exotic plant ecological indicator, which is described a companion paper in this special issue journal. A key aspect of the CEM is that it is a general ecological model that can be tailored to specific cases and species, as the details of any invasion are unique to that invasive species. Our model encompasses the temporal and spatial changes that characterize invasion, identifying the general conditions that allow a species to become invasive in a de novo environment; it then enumerates the possible effects exotic species may have collectively and individually at varying scales and for different ecosystem properties, once a species becomes invasive. The model provides suites of characteristics and processes, as well as hypothesized causal relationships to consider when thinking about the effects or potential effects of an invasive exotic and how restoration efforts will affect these characteristics and processes. In order to illustrate how to use the model as a blueprint for applying a similar approach to other invasive species and ecosystems, we give two examples of using this conceptual model to evaluate the status of two south Florida invasive exotic plant species (melaleuca and Old World climbing fern) and consider potential impacts of these invasive species on restoration.

Howard Johnson's: Rise and Fall of an American Icon

The Howard Johnson’s restaurant chain was one of the first franchise success stories in the United States. Climbing in size to be over 1,000 restaurants, the chain today boasts fewer than 30 units. How could such a successful company spiral downward to virtually nothing? This article examines the history of the chain and offers reasons for its success and demise.

Rigid and Non-rigid Point-based Medical Image Registration

The primary goal of this dissertation is to develop point-based rigid and non-rigid image registration methods that have better accuracy than existing methods. We first present point-based PoIRe, which provides the framework for point-based global rigid registrations. It allows a choice of different search strategies including (a) branch-and-bound, (b) probabilistic hill-climbing, and (c) a novel hybrid method that takes advantage of the best characteristics of the other two methods. We use a robust similarity measure that is insensitive to noise, which is often introduced during feature extraction. We show the robustness of PoIRe using it to register images obtained with an electronic portal imaging device (EPID), which have large amounts of scatter and low contrast. To evaluate PoIRe we used (a) simulated images and (b) images with fiducial markers; PoIRe was extensively tested with 2D EPID images and images generated by 3D Computer Tomography (CT) and Magnetic Resonance (MR) images. PoIRe was also evaluated using benchmark data sets from the blind retrospective evaluation project (RIRE). We show that PoIRe is better than existing methods such as Iterative Closest Point (ICP) and methods based on mutual information. We also present a novel point-based local non-rigid shape registration algorithm. We extend the robust similarity measure used in PoIRe to non-rigid registrations adapting it to a free form deformation (FFD) model and making it robust to local minima, which is a drawback common to existing non-rigid point-based methods. For non-rigid registrations we show that it performs better than existing methods and that is less sensitive to starting conditions. We test our non-rigid registration method using available benchmark data sets for shape registration. Finally, we also explore the extraction of features invariant to changes in perspective and illumination, and explore how they can help improve the accuracy of multi-modal registration. For multimodal registration of EPID-DRR images we present a method based on a local descriptor defined by a vector of complex responses to a circular Gabor filter.

Stated versus observed performance levels in patients with chronic low back pain

This study examined the relationship between chronic low back pain (CLBP) patients' perceived (stated) levels of function and their measured (observed) performance in squatting and stair climbing activities as compared to healthy volunteers. Twenty patients with CLBP and 20 healthy subjects were asked through an interview to self-assess their ability to comfortably perform stair climbing and squatting as well as other tolerances. The subjects were then asked to perform the activities and their performance levels were recorded. Results of the t-tests and Analysis of Variance (ANOVA) procedures revealed that patients' estimate of squatting and stair climbing abilities as well as their demonstrated levels were significantly lower (p < 0.001) than those of the healthy subjects. There was a significant difference between groups in terms of the time required to perform squatting but not stair climbing. Both healthy subjects and patients with CLBP underestimated their physical capabilities. Findings indicate that the use of actual performance measurement combined with self-report of functional abilities is needed when assessing performance levels of both healthy as well as patients with CLBP.

Seguridad en prácticas de andinismo : formación docente en Educación Física

El Profesorado de Educación Física con Orientación en Actividades Regionales en Montaña de la Universidad Nacional del Comahue. (En adelante PEF-CRUB-UNCo) es el único en el país que posee una trayectoria con más de 20 años de formación de profesores de Educación Física con orientación. Fue a través de un trabajo dinámico y continuo a lo largo de los años que se fueron definiendo qué contenidos teórico-prácticos eran los apropiados para la Educación Física (Palacio, López, Schneider, 2011). Se observan coincidencias con las experiencias realizadas en otros Países como España y Alemania en los que las actividades de escalada forman parte de la Formación Docente y de la currícula educativa (Saez Padilla, Gimenez, Fuentes Guerra 2005; Arribas Cubero 2008; Winter, 2000). Se determinó en paralelo con otros autores (Hepp, Güllich y Heidorn, 2001) que los contenidos relacionados con Trekking y Escalada son apropiados para desarrollar en un profesorado de estas características. Una preocupación permanente que desafía a la actividad como contenido educativo es el manejo de las condiciones de seguridad. En el presente trabajo se explicarán las condiciones de Seguridad que a lo largo de los años desde la experiencia, la interrogación permanente, la consulta de bibliografía especializada y las acciones realizadas en la formación docente han sido recopiladas.

Seguridad en prácticas de andinismo : formación docente en Educación Física

El Profesorado de Educación Física con Orientación en Actividades Regionales en Montaña de la Universidad Nacional del Comahue. (En adelante PEF-CRUB-UNCo) es el único en el país que posee una trayectoria con más de 20 años de formación de profesores de Educación Física con orientación. Fue a través de un trabajo dinámico y continuo a lo largo de los años que se fueron definiendo qué contenidos teórico-prácticos eran los apropiados para la Educación Física (Palacio, López, Schneider, 2011). Se observan coincidencias con las experiencias realizadas en otros Países como España y Alemania en los que las actividades de escalada forman parte de la Formación Docente y de la currícula educativa (Saez Padilla, Gimenez, Fuentes Guerra 2005; Arribas Cubero 2008; Winter, 2000). Se determinó en paralelo con otros autores (Hepp, Güllich y Heidorn, 2001) que los contenidos relacionados con Trekking y Escalada son apropiados para desarrollar en un profesorado de estas características. Una preocupación permanente que desafía a la actividad como contenido educativo es el manejo de las condiciones de seguridad. En el presente trabajo se explicarán las condiciones de Seguridad que a lo largo de los años desde la experiencia, la interrogación permanente, la consulta de bibliografía especializada y las acciones realizadas en la formación docente han sido recopiladas.

Leaving and Coming Back to Canada : Evidence from Longitudinal Data (Working Paper 32)

The paper exploits the unique strengths of Statistics Canada's Longitudinal Administrative Database ("LAD"), constructed from individuals' tax records, to shed new light on the extent and nature of the emigration of Canadians to other countries and their patterns of return over the period 1982-1999. The empirical evidence begins with some simple graphs of the overall rates of leaving over time, and follows with the presentation of the estimation results of a model that essentially addresses the question: "who moves?" The paper then analyses the rates of return for those observed to leave the country - something for which there is virtually no existing evidence. Simple return rates are reported first, followed by the results of a hazard model of the probability of returning which takes into account individuals' characteristics and the number of years they have already been out of the country. Taken together, these results provide a new empirical basis for discussions of emigration in general, and the brain drain in particular. Of particular interest are the ebb and flow of emigration rates observed over the last two decades, including a perhaps surprising turndown in the most recent years after climbing through the earlier part of the 1990s; the data on the number who return after leaving, the associated patterns by income level, and the increases observed over the last decade.

Efficient Learning of Bayesian Networks with Bounded Tree-width

Learning Bayesian networks with bounded tree-width has attracted much attention recently, because low tree-width allows exact inference to be performed efficiently. Some existing methods \cite{korhonen2exact, nie2014advances} tackle the problem by using $k$-trees to learn the optimal Bayesian network with tree-width up to $k$. Finding the best $k$-tree, however, is computationally intractable. In this paper, we propose a sampling method to efficiently find representative $k$-trees by introducing an informative score function to characterize the quality of a $k$-tree. To further improve the quality of the $k$-trees, we propose a probabilistic hill climbing approach that locally refines the sampled $k$-trees. The proposed algorithm can efficiently learn a quality Bayesian network with tree-width at most $k$. Experimental results demonstrate that our approach is more computationally efficient than the exact methods with comparable accuracy, and outperforms most existing approximate methods.

Barn utforskar sin förskolegård : Förskolebarns perspektiv på sin utemiljö

Vårt intresse för utemiljön uppstod då vi såg, genom erfarenheter av arbete på förskolor, att många förskolegårdar inte alltid tilltalade barnen. Några gårdar såg inte inspirerande ut och barnen visste inte vet vad de skulle göra. Syftet med studien är att skapa kunskap om hur barn utforskar sin förskolegård och vad som styr deras val av hur de placerar sig själva på gården när de leker. Utifrån en etnografisk, induktiv studie, vill vi lyfta fram vad barnen berättar om sin förskolegård. Vi har utgått från barndomsgeografi vilken ses inom forskningen som en del av barndomssociologin. Barndomen ses här som socialt konstruerad och frågor uppkommer om vilka platser som betraktas som bra för barn. Vi har sett utifrån våra samtalspromenader och observationer att barnen använder sig av olika rörelsestrategier såsom att klättra i träden, åka rutschkana och gunga samt att de använder sig av fysiska aktiviteter som till exempel att bygga kojor, samla naturmaterial och hoppar i lövhögar men att de även styrs av sin nyfikenhet och plötsligt kan stanna till för att titta på insekter etc. när de utforskar områden på gården. Resultaten av vår studie visar att rörelse är något som barnen ofta berättar om att de ägnar sig åt på sin förskolegård.

No Woman's Land

Willkommen Damen and Gentlemen! Roll up, stroll in and join us on a spectacular stagger through the post-apocalyptical wasteland of 1945. Before your very eyes the bearded ladies run on treadmills as they conjure up past and present digital landscapes. Masquerading as men for your entertainment, and their own protection, the bearded duo use gallows humour to launch you on an unimaginable, unconceivable plight of flight and migration. 1945. Lucia Rippel, expelled from her place of birth, walked 220 miles across the fractured landscape of Europe, with her two children and all her belongings dragged in a cart. In 2015, Ildikó Rippel and Rosie Garton retraced her footsteps, crossing borders, climbing fences, bleeding, crying, and blistering, and carrying their flat-pack children. No Woman’s Land is a politically charged, darkly humorous nod to 1920’s Kabarett, entwining the duo’s experience of the walk with Lucia’s story.

Multiple-Retrieval Case-Based Reasoning for Course Timetabling Problems

The structured representation of cases by attribute graphs in a Case-Based Reasoning (CBR) system for course timetabling has been the subject of previous research by the authors. In that system, the case base is organised as a decision tree and the retrieval process chooses those cases which are sub attribute graph isomorphic to the new case. The drawback of that approach is that it is not suitable for solving large problems. This paper presents a multiple-retrieval approach that partitions a large problem into small solvable sub-problems by recursively inputting the unsolved part of the graph into the decision tree for retrieval. The adaptation combines the retrieved partial solutions of all the partitioned sub-problems and employs a graph heuristic method to construct the whole solution for the new case. We present a methodology which is not dependant upon problem specific information and which, as such, represents an approach which underpins the goal of building more general timetabling systems. We also explore the question of whether this multiple-retrieval CBR could be an effective initialisation method for local search methods such as Hill Climbing, Tabu Search and Simulated Annealing. Significant results are obtained from a wide range of experiments. An evaluation of the CBR system is presented and the impact of the approach on timetabling research is discussed. We see that the approach does indeed represent an effective initialisation method for these approaches.