On equivalence classes in iterative learning control

This paper advocates a new approach to study the relation between causal iterative learning control (ILC) and conventional feedback control. Central to this approach is the introduction of the set of admissible pairs (of operators) defined with respect to a family of iterations. Considered are two problem settings: standard ILC, which does not include a current cycle feedback (CCF) term and CCF-ILC, which does. By defining an equivalence relation on the set of admissible pairs, it is shown that in the standard ILC problem there exists a bijective map between the induced equivalence classes and the set of all stabilizing controllers. This yields the well-known Youla parameterization as a corollary. These results do not extend in full generality to the case of CCF-ILC; though gain every admissible pair defines a stabilizing equivalent controller, the converse is no longer true in general

Observations of quasar host galaxies with laser guide star AO

We report on observations of two quasar host galaxies made with the Lick Observatory adaptive optic system using a laser guide star tuned to the wavelength of the sodium D lines. A brief outline of the system is given, and a description of its performance when obtaining science data. We discuss techniques for obtaining calibration of the point spread function and the analysis steps required to obtain useful scientific results. We present H-band images of quasar host galaxies made with the system. Estimates of the host galaxy magnitudes and central black hole masses were made from these data. These are the first observations of quasar host galaxies with a sodium laser guide star

Interpreting idioms in a second language:The role of context and transfer in interpreting English idioms by native Dutch speakers

How do people understand figurative speech in a foreign language? What strategies do they use? By means of an online questionnaire, this study investigated to what extent contextual information and transfer play a role in the interpretation of idioms in a second language, controlling for familiarity. Sixty-one native speakers of Dutch were asked to guess the correct interpretation of English idioms with and without a Dutch equivalent, presented with and without context, out of four answer options. The results showed that correctly interpreting an idiom depends on both the presence of context and the possibility of transfer. More correct interpretations were given when an idiom was presented in a context, but only for English idioms without an equivalent in the native language. English idioms with an equivalent in Dutch, often rated as familiar, were mostly understood correctly. We interpret this result as the involvement of transfer from the native language

The association between muscle strength and activity limitations in patients with the hypermobility type of Ehlers–Danlos syndrome : the impact of proprioception

Purpose: The patients diagnosed with Ehlers-Danlos Syndrome Hypermobility Type (EDS-HT) are characterized by pain, proprioceptive inacuity, muscle weakness, potentially leading to activity limitations. In EDS-HT, a direct relationship between muscle strength, proprioception and activity limitations has never been studied. The objective of the study was to establish the association between muscle strength and activity limitations and the impact of proprioception on this association in EDS-HT patients. Methods: Twenty-four EDS-HT patients were compared with 24 controls. Activity limitations were quantified by Health Assessment Questionnaire (HAQ), Six-Minute Walk test (6MWT) and 30-s chair-rise test (30CRT). Muscle strength was quantified by handheld dynamometry. Proprioception was quantified by movement detection paradigm. In analyses, the association between muscle strength and activity limitations was controlled for proprioception and confounders. Results: Muscle strength was associated with 30CRT (r = 0.67, p = <0.001), 6MWT (r = 0.58, p = <0.001) and HAQ (r = 0.63, p = <0.001). Proprioception was associated with 30CRT (r = 0.55, p <0.001), 6MWT (r = 0.40, p = <0.05) and HAQ (r = 0.46, p < 0.05). Muscle strength was found to be associated with activity limitations, however, proprioceptive inacuity confounded this association. Conclusions: Muscle strength is associated with activity limitations in EDS-HT patients. Joint proprioception is of influence on this association and should be considered in the development of new treatment strategies for patients with EDS-HT. Implications for rehabilitation : Reducing activity limitations by enhancing muscle strength is frequently applied in the treatment of EDS-HT patients. Although evidence regarding treatment efficacy is scarce, the current paper confirms the rationality that muscle strength is an important factor in the occurrence of activity limitations in EDS-HT patients. Although muscle strength is the most dominant factor that is associated with activity limitations, this association is confounded by proprioception. In contrast to common belief proprioception was not directly associated with activity limitations but confounded this association. Controlling muscle strength on the bases of proprioceptive input may be more important for reducing activity limitations than just enhancing sheer muscle strength

A systematic design approach for objectifying Building with Nature solutions

Hydraulic engineering infrastructure is supposed to keep functioning for many years and is likely to interfere with both the natural and the social environment at various scales. Due to its long life-cycle, hydraulic infrastructure is bound to face changing environmental conditions as well as changes in societal views on acceptable solutions. This implies that sustainability and adaptability are/should be important attributes of the design, the development and operation of hydraulic engineering infrastructure. Sustainability and adaptability are central to the Building with Nature (BwN) approach. Although nature-based design philosophies, such as BwN, have found broad support, a key issue that inhibits a wider mainstream implementation is the lack of a method to objectify BwN concepts. With objectifying, we mean turning the implicit into an explicit engineerable ‘object’, on the one hand, and specifying clear design ‘objectives’, on the other. This paper proposes the “Frame of Reference” approach as a method to systematically transform BwN concepts into functionally specified engineering designs. It aids the rationalisation of BwN concepts and facilitates the transfer of crucial information between project development phases, which benefits the uptake, acceptance and eventually the successful realisation of BwN solutions. It includes an iterative approach that is well suited for assessing status changes of naturally dynamic living building blocks of BwN solutions. The applicability of the approach is shown for a case that has been realised in the Netherlands. Although the example is Dutch, the method, as such, is generically applicable