Anisotropy for spatial summation of elongated patches of grating:A tale of two tails

Studies of spatial summation often use sinusoidal gratings with blurred edges. When the envelope is elongated (i) along the grating stripes and (ii) at right angles to the grating stripes, we refer to the stimuli as skunk-tails and tiger-tails respectively. Previous work [Polat & Tyler, 1999; Vision Research, 39, 887-895.] has found that sensitivity to skunk-tails is greater than for tiger-tails, but there have been several failures to replicate this result within a subset of the conditions. To address this we measured detection thresholds for skunk-tails, tiger-tails and squares of grating with sides matched to the lengths of the tails. For foveal viewing, we found a contrast sensitivity advantage in the order of 2 dB for skunk-tails over tiger-tails, but only for horizontal gratings. For vertical gratings, sensitivity was very similar for both tail-types. When the stimuli were presented parafoveally (upper right visual field), a small advantage was found for skunk-tails over tiger-tails at both orientations, and spatial summation slopes were close to that of the ideal observer. We did not replicate the findings of Polat & Tyler, but our results are consistent with (i) those of Foley et al. [Foley, J. M., Varadharajan, S., Koh, C. C., & Farias, C. Q. (2007) Vision Research, 47, 85-107.] who used only vertical gratings and (ii) those from modelfest, where only horizontal gratings were used. The small effect of tail-type here suggests an anisotropy in the underlying physiology. © 2007 Elsevier Ltd. All rights reserved.

Zero-dimensional noise:the best mask you never saw

The transmission of weak signals through the visual system is limited by internal noise. Its level can be estimated by adding external noise, which increases the variance within the detecting mechanism, causing masking. But experiments with white noise fail to meet three predictions: (a) noise has too small an influence on the slope of the psychometric function, (b) masking occurs even when the noise sample is identical in each two-alternative forced-choice (2AFC) interval, and (c) double-pass consistency is too low. We show that much of the energy of 2D white noise masks extends well beyond the pass-band of plausible detecting mechanisms and that this suppresses signal activity. These problems are avoided by restricting the external noise energy to the target mechanisms by introducing a pedestal with a mean contrast of 0% and independent contrast jitter in each 2AFC interval (termed zero-dimensional [0D] noise). We compared the jitter condition to masking from 2D white noise in double-pass masking and (novel) contrast matching experiments. Zero-dimensional noise produced the strongest masking, greatest double-pass consistency, and no suppression of perceived contrast, consistent with a noisy ideal observer. Deviations from this behavior for 2D white noise were explained by cross-channel suppression with no need to appeal to induced internal noise or uncertainty. We conclude that (a) results from previous experiments using white pixel noise should be re-evaluated and (b) 0D noise provides a cleaner method for investigating internal variability than pixel noise. Ironically then, the best external noise stimulus does not look noisy.

[Review of] Ivo Mijnssen, The Quest for an Ideal Youth in Putin’s Russia I. Back to Our Future! History, Modernity and Patriotism According to Nashi, 2005–2012. Soviet and Post-Soviet Politics and Society, Stuttgart: Ibidem Verlag, 2012, 202pp., e 34.90 p/b

THE YOUTH MOVEMENT NASHI (OURS) WAS FOUNDED IN THE SPRING of 2005 against the backdrop of Ukraine’s ‘Orange Revolution’. Its aim was to stabilise Russia’s political system and take back the streets from opposition demonstrators. Personally loyal to Putin and taking its ideological orientation from Surkov’s concept of ‘sovereign democracy’, Nashi has sought to turn the tide on ‘defeatism’ and develop Russian youth into a patriotic new elite that ‘believes in the future of Russia’ (p. 15). Combining a wealth of empirical detail and the application of insights from discourse theory, Ivo Mijnssen analyses the organisation’s development between 2005 and 2012. His analysis focuses on three key moments—the organisation’s foundation, the apogee of its mobilisation around the Bronze Soldier dispute with Estonia, and the 2010 Seliger youth camp—to help understand Nashi’s organisation, purpose and ideational outlook as well as the limitations and challenges it faces. As such,the book is insightful both for those with an interest in post-Soviet Russian youth culture, and for scholars seeking a rounded understanding of the Kremlin’s initiatives to return a sense of identity and purpose to Russian national life.The first chapter, ‘Background and Context’, outlines the conceptual toolkit provided by Ernesto Laclau and Chantal Mouffe to help make sense of developments on the terrain of identity politics. In their terms, since the collapse of the Soviet Union, Russia has experienced acute dislocation of its identity. With the tangible loss of great power status, Russian realities have become unfixed from a discourse enabling national life to be constructed, albeit inherently contingently, as meaningful. The lack of a Gramscian hegemonic discourse to provide a unifying national idea was securitised as an existential threat demanding special measures. Accordingly, the identification of those who are ‘notUs’ has been a recurrent theme of Nashi’s discourse and activity. With the victory in World War II held up as a foundational moment, a constitutive other is found in the notion of ‘unusual fascists’. This notion includes not just neo-Nazis, but reflects a chain of equivalence that expands to include a range of perceived enemies of Putin’s consolidation project such as oligarchs and pro-Western liberals.The empirical background is provided by the second chapter, ‘Russia’s Youth, the Orange Revolution, and Nashi’, which traces the emergence of Nashi amid the climate of political instability of 2004 and 2005. A particularly note-worthy aspect of Mijnssen’s work is the inclusion of citations from his interviews with Nashicommissars; the youth movement’s cadres. Although relatively few in number, such insider conversations provide insight into the ethos of Nashi’s organisation and the outlook of those who have pledged their involvement. Besides the discussion of Nashi’s manifesto, the reader thus gains insight into the motivations of some participants and behind-the-scenes details of Nashi’s activities in response to the perceived threat of anti-government protests. The third chapter, ‘Nashi’s Bronze Soldier’, charts Nashi’s role in elevating the removal of a World War II monument from downtown Tallinn into an international dispute over the interpretation of history. The events subsequent to this securitisation of memory are charted in detail, concluding that Nashi’s activities were ultimately unsuccessful as their demands received little official support.The fourth chapter, ‘Seliger: The Foundry of Modernisation’, presents a distinctive feature of Mijnssen’s study, namely his ethnographic account as a participant observer in the Youth International Forum at Seliger. In the early years of the camp (2005–2007), Russian participants received extensive training, including master classes in ‘methods of forestalling mass unrest’ (p. 131), and the camp served to foster a sense of group identity and purpose among activists. After 2009 the event was no longer officially run as a Nashi camp, and its role became that of a forum for the exchange of ideas about innovation, although camp spirit remained a central feature. In 2010 the camp welcomed international attendees for the first time. As one of about 700 international participants in that year the author provides a fascinating account based on fieldwork diaries.Despite the polemical nature of the topic, Mijnssen’s analysis remains even-handed, exemplified in his balanced assessment of the Seliger experience. While he details the frustrations and disappointments of the international participants with regard to the unaccustomed strict camp discipline, organisational and communication failures, and the controlled format of many discussions,he does not neglect to note the camp’s successes in generating a gratifying collective dynamic between the participants, even among the international attendees who spent only a week there.In addition to the useful bibliography, the book is back-ended by two appendices, which provide the reader with important Russian-language primary source materials. The first is Nashi’s ‘Unusual Fascism’ (Neobyknovennyi fashizm) brochure, and the second is the booklet entitled ‘Some Uncomfortable Questions to the Russian Authorities’ (Neskol’ko neudobnykh voprosov rossiiskoivlasti) which was provided to the Seliger 2010 instructors to guide them in responding to probing questions from foreign participants. Given that these are not readily publicly available even now, they constitute a useful resource from the historical perspective.

Theory of hybrid computational and physical measurement-based integration of thermal and dimensional measurement

In dimensional metrology, often the largest source of uncertainty of measurement is thermal variation. Dimensional measurements are currently scaled linearly, using ambient temperature measurements and coefficients of thermal expansion, to ideal metrology conditions at 20˚C. This scaling is particularly difficult to implement with confidence in large volumes as the temperature is unlikely to be uniform, resulting in thermal gradients. A number of well-established computational methods are used in the design phase of product development for the prediction of thermal and gravitational effects, which could be used to a greater extent in metrology. This paper outlines the theory of how physical measurements of dimension and temperature can be combined more comprehensively throughout the product lifecycle, from design through to the manufacturing phase. The Hybrid Metrology concept is also introduced: an approach to metrology, which promises to improve product and equipment integrity in future manufacturing environments. The Hybrid Metrology System combines various state of the art physical dimensional and temperature measurement techniques with established computational methods to better predict thermal and gravitational effects.

A Luenberger state observer for stator resistance estimation in sensorless induction motor drives

The primary objective of this paper is to elimination of the problem of sensitivity to parameter variation of induction motor drive. The proposed sensorless strategy is based on an algorithm permitting a better simultaneous estimation of the rotor speed and the stator resistance including an adaptive mechanism based on the lyaponov theory. To study the reliability and the robustness of the sensorless technique to abnormal operations, some simulation tests have been performed under several cases. The proposed sensorless vector control scheme showed a good performance behavior in the transient and steady states, with an excellent disturbance rejection of the load torque. © 2013 Praise Worthy Prize S.r.l. - All rights reserved.