Home About us Contact
|
Home About us Contact | ||
|
|
||
Role Similar (role + similar)
Selected AbstractsAnti-windup synthesis for nonlinear dynamic inversion control schemesINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 13 2010G. Herrmann Abstract A general anti-windup (AW) compensation scheme is provided for a class of input constrained feedback-linearizable nonlinear systems. The controller considered is an inner-loop nonlinear dynamic inversion controller, augmented with an outer-loop linear controller, of arbitrary structure. For open-loop globally exponentially stable plants, it is shown that (i) there always exists a globally stabilizing AW compensator corresponding to a nonlinear generalization of the Internal-Model-Control (IMC) AW solution; (ii) important operator theoretic parallels exist between the AW design scheme for linear control and the suggested AW design scheme for nonlinear affine plants and (iii) a more attractive AW compensator may be obtained by using a nonlinear state-feedback term, which plays a role similar to the linear state-feedback term in linear coprime factor-based AW compensation. The results are demonstrated on a dual-tank simulation example. Copyright © 2009 John Wiley & Sons, Ltd. [source] Changes of taxonomic and trophic structure of fish assemblages along an environmental gradient in the Upper Beni watershed (Bolivia)JOURNAL OF FISH BIOLOGY, Issue 1 2006M. Pouilly The distribution and the diet of 28 fish species were evaluated, during the dry season, in 12 streams of the Upper Beni watershed (Amazon basin, Bolivia). The 12 streams were of similar size (stream width and water depth) but situated on a gradient of altitude in the Andean and sub-Andean areas. The environmental conditions in the stream changed in relation to the altitude. As altitude decreased, slope and water velocity also decreased, while temperature, conductivity, pH and the proportion of pools increased. Although the diets of the species were mainly based on two aquatic autochthonous food resources, invertebrates and sediment, species were classified into five trophic guilds: detritivores, algivores, piscivores, invertivores-omnivores and aquatic specialist invertivores. In all streams invertivores dominated or co-dominated with detritivores. The trophic structure of the assemblages, however, changed in relation to the environmental gradient. The fish species richness increased and the trophic composition became more diverse at lower altitudes, when slope decreased and temperature increased. At the same time, the relative number of invertivore species decreased, whereas the relative number of detritivore, algivore and piscivore species increased. Decreasing altitude appeared to play a role similar to increasing stream size along the longitudinal gradient. This could be explained by geomorphological and temperature variations that may generate environmental conditions favourable to an increase of productivity. [source] Hamstrings and iliotibial band forces affect knee kinematics and contact patternJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 1 2000S. D. Kwak Many clinical studies have emphasized the role of the hamstrings and the iliotibial band on knee mechanics, although few biomechanical studies have investigated it. This study therefore examined two hypotheses: (a) with loading of the hamstrings, the tibia translates posteriorly and rotates externally and the tibial contact pattern shifts anteriorly; furthermore, the changes in tibial kinematics alter patellar kinematics and contact; and (b) loading the iliotibial band alters the kinematics and contact pattern of the tibiofemoral joint similarly to loading the hamstrings, and loading the iliotibial band laterally translates the patella and its contact location. Five cadaveric knee specimens were tested with a specially designed knee-joint testing machine in an open-chain configuration. At various flexion angles, the knees were tested always with a quadriceps force but with and without a hamstrings force and with and without an iliotibial band force. The results support the first hypothesis. Hence, the hamstrings may be important anterior and rotational stabilizers of the tibia, a role similar to that of the anterior cruciate ligament. The results also support the second hypothesis, although the iliotibial band force had a smaller effect on the tibia than did the hamstrings force. Both forces also changed patellar kinematics and contact, demonstrating that these structures should also be considered during the clinical management of patellar disorders. [source] Words from Nowhere , Limits of CriticismPHILOSOPHICAL INVESTIGATIONS, Issue 2 2008Steinar Bøyum In the present essay, I aim to accentuate an analogy between the patterns of thought articulated by Berkeley's Hylas and those of Nagel in his philosophy of bats and aliens. The comparison has a critical purpose, with Philonous playing a role similar to that of Wittgenstein. I argue that Nagel's central claim comes down to statements that are marked by a peculiar form of emptiness. Towards the end, though, I will concede that this kind of Wittgensteinian criticism runs up against certain limits. The fantasies produced by Hylas or Nagel have as counterparts genuine philosophical expressions of experience, which are not vulnerable to the charges levelled at their theoretical parallels. [source] THE SOUTHERN AGRARIANS, PROGRESS, AND THE TRAGIC VOICEPOLITICS & POLICY, Issue 1 2001Christopher M. Duncan In this argument the Agrarian role in the American political drama is not necessarily the specific one implied by the dichotomy: "Agrarian versus Industrial" (Twelve Southerners [1930] 1977, xxxviii), or the policist pronouncement", that the culture of the soil is the best, and that therefore it should have the economic preference and enlist the maximum number of workers"(xlvii). Instead, this is an attempt to place them in a role similar to that played by Sophocles' Antigone,and Sophocles himself,juxtaposing them to the North's Creon. I argue that the Southern Agrarian "voice," when heard properly, makes, possible the tragic sense, adjured by America's unequivocal attachment to modernity's gospel of progress. By positioning the Agrarians in such a way the goal is to point out a way of thinking about the political world, to create a sensibility that is only possible when their voice or another like it is heard properly and with its own timbre. If the project is successful, then two aims will be realized. First, the place and role of the Southern Agrarians in the history of American political thought will be made clearer. And secondly, the history of American political thought will have been employed in part as a kind of theoretical advocacy in the service of American political theory. [source] Putative Role of Carbon Monoxide Signaling Pathway in Penile Erectile FunctionTHE JOURNAL OF SEXUAL MEDICINE, Issue 1 2009Mohamed T. Abdel Aziz MD ABSTRACT Introduction., Erectile response depends on nitric oxide (NO) generated by NO synthase (NOS) enzyme of the nerves and vascular endothelium in the cavernous tissue. NO activates soluble guanylate cyclase (sGC), leading to the production of cyclic guanosine monophosphate (cGMP). cGMP activates cGMP-dependent protein kinase that activates Ca2+/ATPase pump that activates Ca2+/K efflux pump extruding Ca2+ across the plasma membrane with consequent smooth muscle cell relaxation. A role similar to that of NOS/NO signaling has been postulated for carbon monoxide (CO) produced in mammals from heme catabolism by heme oxygenase (HO) enzyme. Aim., To assess CO signaling pathway for erectile function by reviewing published studies. Methods., A systematic review of published studies on this affair based on Pubmed and Medical Subject Heading databases, with search for all concerned articles. Main Outcome Measures., Documentation of positive as well as negative criteria of CO/HO signaling focused on penile tissue. Results., The concept that HO-derived CO could play a role in mediating erectile function acting in synergism with, or as a potentiator for, NOS/NO signaling pathway is gaining momentum. CO/HO signaling pathway has been shown to partially mediate the actions of oral phosphodiesterase type 5 inhibitors. In addition, it was shown that the use of CO releasing molecules potentiated cavernous cGMP levels. However, increased CO production or release was reported to be associated, in some studies, with vasoconstriction. Conclusion., This review sheds a light on the significance of cavernous tissue CO signaling pathway that may pave the way for creation of therapeutic modalities based on this pathway. Abdel Aziz MT, Mostafa T, Atta H, Wassef MA, Fouad HH, Rashed LA, and Sabry D. Putative role of carbon monoxide signaling pathway in penile erectile function. J Sex Med 2009;6:49,60. [source] Conservation of a conformational switch in RadA recombinase from Methanococcus maripaludisACTA CRYSTALLOGRAPHICA SECTION D, Issue 6 2009Yang Li Archaeal RadAs are close homologues of eukaryal Rad51s (,40% sequence identity). These recombinases promote ATP hydrolysis and a hallmark strand-exchange reaction between homologous single-stranded and double-stranded DNA substrates. Pairing of the 3,-overhangs located at the damaged DNA with a homologous double-stranded DNA enables the re-synthesis of the damaged region using the homologous DNA as the template. In recent studies, conformational changes in the DNA-interacting regions of Methanococcus voltae RadA have been correlated with the presence of activity-stimulating potassium or calcium ions in the ATPase centre. The series of crystal structures of M. maripaludis RadA presented here further suggest the conservation of an allosteric switch in the ATPase centre which controls the conformational status of DNA-interacting loops. Structural comparison with the distant Escherichia coli RecA homologue supports the notion that the conserved Lys248 and Lys250 residues in RecA play a role similar to that of cations in RadA. The conservation of a cationic bridge between the DNA-interacting L2 region and the terminal phosphate of ATP, together with the apparent stability of the nucleoprotein filament, suggests a gap-displacement model which may explain the advantage of ATP hydrolysis for DNA-strand exchange. [source] | ||||||||||