Optimally Sparse Frames

Frames have established themselves as a means to derive redundant, yet stable decompositions of a signal for analysis or transmission, while also promoting sparse expansions. However, when the signal dimension is large, the computation of the frame measurements of a signal typically requires a large number of additions and multiplications, and this makes a frame decomposition intractable in applications with limited computing budget. To address this problem, in this paper, we focus on frames in finite-dimensional Hilbert spaces and introduce sparsity for such frames as a new paradigm. In our terminology, a sparse frame is a frame whose elements have a sparse representation in an orthonormal basis, thereby enabling low-complexity frame decompositions. To introduce a precise meaning of optimality, we take the sum of the numbers of vectors needed of this orthonormal basis when expanding each frame vector as sparsity measure. We then analyze the recently introduced algorithm Spectral Tetris for construction of unit norm tight frames and prove that the tight frames generated by this algorithm are in fact optimally sparse with respect to the standard unit vector basis. Finally, we show that even the generalization of Spectral Tetris for the construction of unit norm frames associated with a given frame operator produces optimally sparse frames

Reference Production as Search:The Impact of Domain Size on the Production of Distinguishing Descriptions

When producing a description of a target referent in a visual context, speakers need to choose a set of properties that distinguish it from its distractors. Computational models of language production/generation usually model this as a search process and predict that the time taken will increase both with the number of distractors in a scene and with the number of properties required to distinguish the target. These predictions are reminiscent of classic ndings in visual search; however, unlike models of reference production, visual search models also predict that search can become very e cient under certain conditions, something that reference production models do not consider. This paper investigates the predictions of these models empirically. In two experiments, we show that the time taken to plan a referring expression { as re ected by speech onset latencies { is in uenced by distractor set size and by the number of properties required, but this crucially depends on the discriminability of the properties under consideration. We discuss the implications for current models of reference production and recent work on the role of salience in visual search.peer-reviewe

Production of referring Eexpressions (PRE-CogSci) 2009 : bridging the gap between computational and empirical approaches to reference

How do speakers refer to entities? This question has been addressed by both psycholinguists and computational linguists. A referring expression is typically defined as one which is produced in order to identify an object or set of objects for a listener or reader, in a relevant domain of discourse. In spite of several decades of research on the topic, our understanding of it is still incomplete, in part due to a lack of communication between psycholinguists and computational linguists, a remarkable state of affairs given the substantial overlap in the topics that these practitioners have investigated. Among these topics, the following have stood out in recent years: Over- and underspecification: Why and how do speakers overspecify when they produce referring expressions? Under what conditions do they underspecify?peer-reviewe

Conceptualization in reference production:Probabilistic modeling and experimental testing

In psycholinguistics, there has been relatively little work investigating conceptualization-how speakers decide which concepts to express. This contrasts with work in natural language generation (NLG), a subfield of artificial intelligence, where much research has explored content determination during the generation of referring expressions. Existing NLG algorithms for conceptualization during reference production do not fully explain previous psycholinguistic results, so we developed new models that we tested in three language production experiments. In our experiments, participants described target objects to another participant. In Experiment 1, either size, color, or both distinguished the target from all distractor objects; in Experiment 2, either color, type, or both color and type distinguished it from all distractors; In Experiment 3, color, size, or the border around the object distinguished the target. We tested how well the different models fit the distribution of description types (e.g., "small candle," "gray candle," "small gray candle") that participants produced. Across these experiments, the probabilistic referential overspecification model (PRO) provided the best fit. In this model, speakers first choose a property that rules out all distractors. If there is more than one such property, then they probabilistically choose one on the basis of a preference for that property. Next, they sometimes add another property, with the probability again determined by its preference and speakers' eagerness to overspecify

Short-Cut Method to Assess a Gross Available Energy in a Medium-Load Screw Friction Press

The present study proposed a rapid method, based on a previous universal compression tests, to estimate the required load capacity to cold forge different specimen quantity in a screw press. Accordingly, experimental and theoretical approach are performed to check new adjustable drive motor of the modified forging machine to achieve a gross available energy to deform the specimens preventing damage of the forging machine. During the forging experiments, two screw friction presses (as-received and modified) are used to validate the theoretical approach. The modified press exhibits an increase of 51% of gross energy and 11% of maximum load capacity compare to the as-received press. This method is used to improve the effective of the forging process avoiding excessive loads that could promote machine failure. Therefore, a low-cost and easy to implement methodology is proposed to determine the energy and load capacity of a screw friction press to forge different specimen quantities with symmetry pattern configurations.This work is supported by the Ministry of Economy and Competitiveness of Spain (reference project: FJCI-2016-29297), Instituto Nacional de Tecnologia Industrial (INTI) of Argentina and the Aeronautics Advanced Manufacturing Center (CFAA) of Bilbao

Cornerstones of Sampling of Operator Theory

This paper reviews some results on the identifiability of classes of operators whose Kohn-Nirenberg symbols are band-limited (called band-limited operators), which we refer to as sampling of operators. We trace the motivation and history of the subject back to the original work of the third-named author in the late 1950s and early 1960s, and to the innovations in spread-spectrum communications that preceded that work. We give a brief overview of the NOMAC (Noise Modulation and Correlation) and Rake receivers, which were early implementations of spread-spectrum multi-path wireless communication systems. We examine in detail the original proof of the third-named author characterizing identifiability of channels in terms of the maximum time and Doppler spread of the channel, and do the same for the subsequent generalization of that work by Bello. The mathematical limitations inherent in the proofs of Bello and the third author are removed by using mathematical tools unavailable at the time. We survey more recent advances in sampling of operators and discuss the implications of the use of periodically-weighted delta-trains as identifiers for operator classes that satisfy Bello's criterion for identifiability, leading to new insights into the theory of finite-dimensional Gabor systems. We present novel results on operator sampling in higher dimensions, and review implications and generalizations of the results to stochastic operators, MIMO systems, and operators with unknown spreading domains

Comparing cancer survivors in population-based samples with those in online cancer communities:Cross-sectional questionnaire study

BACKGROUND: Most Western countries have websites that provide information on cancer and the opportunity to participate in online cancer communities (OCCs). The number of patients with cancer that participate in these OCCs is growing. These patients are relatively easy to approach for research purposes. OBJECTIVE: The objective of this study is to determine the differences and similarities between survivors of cancer in population-based samples and survivors participating in OCCs who use the internet in relation to their illness. METHODS: In 2017, we drew a sample of 539 population-based patients and 531 OCC patients. The population-based patients were sent a paper-based questionnaire, and the OCC patients were sent the same questionnaire on the web. In the questionnaire, we asked patients about their sociodemographics, internet use, sources of information, media use, and wishes regarding future internet use for health care–related purposes, and the effect of internet use on their health care consumption. RESULTS: The response rate of population-based internet users was 47% (233/496), and that of the OCC group was 40.3% (214/531). The OCC group had a significantly higher education level (P<.001), was younger (P<.001), had more survivors that were employed (P<.001), and attached greater importance to the internet (171/214, 79.9% vs 126/233, 54.1%; P<.001) and fellow survivors (107/214, 50% vs 60/233, 25.8%; P<.001). Compared with the population-based group, the OCC group reported more intensive internet use immediately after diagnosis, during treatment, and during follow-up (P<.001 in each case). There were similarities in terms of the relative importance that survivors attach to the various sources of information, the topics on which they seek information, and their wishes for future eHealth possibilities. The OCC group reported a greater need to participate in a web-based class or chat with others (92/214, 43% vs 44/233, 18.9%). CONCLUSIONS: We conclude that survivors who are members of an OCC are not representative of survivors of cancer in general. There are significant differences in sociodemographic characteristics, internet use during their treatment journey, internet search frequency during their cancer journey, and participation wishes. Using web-based information and communication can support shared decision-making and may facilitate the active participation of patients during their treatment. For research purposes, it is important to take the bias in OCC groups into account

Non-deterministic attribute selection in reference production

In producing identifying descriptions, speakers often overspecify and manifest preferences for certain at-tributes. However, current computational models which incorporate this observation tend not to make precise predictions about when and how much speakers do this. The present paper proposes and evaluates two alter-native models, based on the results of a new experi-ment. Unlike current models, the new ones are non-deterministic and seek to make precise quantitative pre-dictions about the extent to which speakers overspecify.peer-reviewe

Are we Bayesian referring expression generators

A recent paper by Frank and Goodman (2012) proposes a Bayesian model of simple referential games. One of the claims embodied in the model is that choosing which word or property to use to refer to an object depends on the utility of the property. In this paper, we compare this model to other computational models of reference production, in particular the recent pro (Probabilistic Referential Overspecification) model. We argue that the assumption of utility that guides property choice in the Frank and Goodman (2012) model is inadequate, insofar as it ignores the possibility of overspecification and the role of preference rankings among properties, as a result of which they may be used irrespective of their utility. We show that models that do take this into account, such as pro, have a better fit to experimental data in which participants have the possibility of overspecifying.peer-reviewe

Does domain size impact speech onset time during reference production?

In referring to a target referent, speakers need to choose a set of properties that jointly distinguish it from its distractors. Current computational models view this as a search process in which the decision to include a prop- erty requires checking how many distractors it excludes. Thus, these models predict that identifying descriptions should take longer to produce the larger the distractor set is, independent of how many properties are required to identify a target. Since every property that is selected is checked, they also predict that distinguishing a tar- get should take longer the more properties are required to distinguish it. This paper tests this prediction em- pirically, contrasting it with two alternative predictions based on models of visual search. Our results provide support for the predictions of computational models, suggesting a crucial di erence between the mechanisms underlying reference production and object identi ca- tion.peer-reviewe