26,721 research outputs found
Inuit Women Artists : Voices from Cape Dorset
No full textTo accompany an exhibition of works by nine Inuit women sculptors and printmakers, texts by Freeman, Leroux and Jackson contextualize the artists, their work, and the exhibition. Individual "portfolios" on each artist provide a biographical career summary, and a text by the artist reflecting on her life. Includes three essays by "modern" Inuit women and a glossary of Inuit terms. Bibl. 3 p
Experimental evaluation of iterative learning control algorithms for non-minimum phase plants
No full textThe purpose of this paper is two-fold, firstly it describes the development and modelling of an experimental test facility as a platform on which to assess the performance of Iterative Learning Control (ILC) schemes. This facility includes a non-minimum phase component. Secondly, P-Type, D-Type and phase-lead types of the algorithm have been implemented on the test-bed, results are presented for each method and their performance is compared. Although all the ILC strategies tested experience eventual divergence when applied to a non-minimum phase system, it is found that there is an optimum phase-lead ILC design that maximizes convergence and minimizes error. A general method of arriving at this phase-lead from knowledge of the plant model is described. A variety of filters have been applied and assessed in order to improve the overall performance of the algorithm
Approaches to the analysis of single beads for Combinatorial chemistry
No full textIn many solid-phase combinatorial syntheses a single bead is taken as representative of a batch of beads. The variability within a batch of beads therefore crucially influences the success of an analytical or synthetic procedure. The determination of the active group loading of individual beads was achieved for thiol derivatised and amine derivatised beads with a detection limit of 0.1 μmol/g resin (NH2) and the protocol subsequently applied to the individual analysis of a sample of beads to achieve a distribution graph of loadings. A low-volume flow-injection colorimetric apparatus was constructed for the analysis of the small sample volumes produced. The data compiled illustrates that the relative standard deviation within a batch of beads an be high, up to 31% from the batches analysed, highlighting the risk associated with using a single bead as a representative of the whole batch. The novel determination of the mass of single beads provided an alternative to gravimetric analysis by mass estimation by chemical means. By successfully combining this approach with a method for the determination of amine sites the loading of single beads was accurately determined. The handling and manipulation of single, and small numbers of resin beads was achieved using a unique low-volume manipulation apparatus specifically designed for this application. A number of the analytical protocols developed were carried out by employing this apparatus greatly improving the ease of handling, and also the throughput time.Apparatus was also developed for the removal of unbound compound from a single bead by electrophoresis. Groups of compounds were driven from the resin beads onto a thin-layer silica chromatography plate within a few seconds, where they could be separated by TLC. Laser confocal microscopy was used to identify the physical structures and characteristics of single resin beads by detection of the emitted fluorescence from a derivatised bead. The images viewed provided information on the consequences of solvent swelling of polymer resins.</p
Phase-lead based iterative learning control implemented experimentally on a non-minimum phase plant
No full textFurther results on the experimental evaluation of iterative learning control algorithms for non-minimum phase plants
No full textThis paper builds on previous work in which simple structure ILC algorithms were experimentally evaluated on a non-minimum phase plant. The phase-lead update law, the most promising of those implemented, is examined using an established performance criterion. The use of a forgetting factor is found to overcome the problem of instability, but at the expense of increased final error. This is verified through experimentation. The phase-lead algorithm is improved using additional phase-leads to remove the instability and improve convergence and final error. This technique is generalized to produce an optimization routine which leads to greatly improved results. The learning law utilizing the plant adjoint is found to fit naturally into this framework and practical results are presented to compare their respective performance. This algorithm, which requires a model of the plant, is reformulated into one which does not. Results are presented using this technique and practical guidelines are produced and tested to improve its performance. A simple method of increasing the learning at higher frequencies is proposed and practical limitations are addressed and verified experimentally. All the algorithms tested are compared with respect to their performance, practicality and robustness
A 2D systems approach to iterative learning control for discrete linear processes with zero Markov parameters
No full textIn this paper a new approach to iterative learning control for the practically relevant case of deterministic discrete linear plants with uniform rank greater than unity is developed. The analysis is undertaken in a 2D systems setting that, by using a strong form of stability for linear repetitive processes, allows simultaneous consideration of both trial-to-trial error convergence and along the trial performance, resulting in design algorithms that can be computed using Linear Matrix Inequalities (LMIs). Finally, the control laws are experimentally verified on a gantry robot that replicates a pick and place operation commonly found in a number of applications to which iterative learning control is applicable
Local two-sample testing: a new tool for analysing high-dimensional astronomical data
No full textModern surveys have provided the astronomical community with a flood of high-dimensional data, but analyses of these data often occur after their projection to lower dimensional spaces. In this work, we introduce a local two-sample hypothesis test framework that an analyst may directly apply to data in their native space. In this framework, the analyst defines two classes based on a response variable of interest (e.g. higher mass galaxies versus lower mass galaxies) and determines at arbitrary points in predictor space whether the local proportions of objects that belong to the two classes significantly differ from the global proportion. Our framework has a potential myriad of uses throughout astronomy; here, we demonstrate its efficacy by applying it to a sample of 2487 i-band-selected galaxies observed by the HST-ACS in four of the CANDELS programme fields. For each galaxy, we have seven morphological summary statistics along with an estimated stellar mass and star formation rate (SFR). We perform two studies: one in which we determine regions of the seven-dimensional space of morphological statistics where high-mass galaxies are significantly more numerous than low-mass galaxies, and vice versa, and another study where we use SFR in place of mass. We find that we are able to identify such regions, and show how high-mass/low-SFR regions are associated with concentrated and undisturbed galaxies, while galaxies in low-mass/high-SFR regions appear more extended and/or disturbed than their high-mass/low-SFR counterparts.
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