U-shaped learning is a learning behaviour in which the learner first learns something, then unlearns it and finally relearns it. Such a behaviour, observed by psychologists, for example, in the learning of past-tenses of English verbs, has been widely discussed among psychologists and cognitive scientists as a fundamental example of the non-monotonicity of learning. Previous theory literature h...

The paper deals with the following problem: is returning to wrong conjectures necessary to achieve full power of algorithmic learning? Returning to wrong conjectures complements the paradigm of U-shaped learning [3,7,9,24,29] when a learner returns to old correct conjectures. We explore our problem for classical models of learning in the limit from positive data: explanatory learning (when a le...

A U-shaped curve in a cognitive-developmental trajectory refers to a three-step process: good performance followed by bad performance followed by good performance once again. U-shaped curves have been observed in a wide variety of cognitive-developmental and learning contexts. U-shaped learning seems to contradict the idea that learning is a monotonic, cumulative process and thus constitutes a ...

Gerontology focuses on deterioration with increasing age, but in most populations most variables, including survival probability, improve at early ages (ontogenescence) before deteriorating at advanced ages (senescence). The extent to which gerontology needs to consider this U-shaped pattern of risk over age depends upon the mechanistic, demographic and evolutionary links and interactions betwe...

A novel compact-sized ultra-wideband (UWB) bandpass filter (BPF) is proposed in this paper. The proposed BPF is highly selective and is able to eliminate WLAN signals from 5.15-5.35 GHz, and downlink of X-band satellite communication signals from 7.25-7.75 GHz. Generally, a multiple-mode resonator (MMR), comprised of a U-shaped line, with two high impedance stubs connected to it, and one steppe...

the environmental kuznets curve (ekc) hypothesis posits an inverted u relationship between environmental pollutants and per capita income. recent researches have examined this hypothesis for different pollutants in different countries. however, so far a few number of ekc studies have been carried out in iran. this might be due to the lack of reliable environmental data in this field. the aim of...