52 research outputs found
Robot-learning using a Tree-based Policy Representation
No full textLearning is an important aspect in creating versatile robots. Pre-programming a robot to acquire a wide variety of skills in an ever changing environment is unfeasible. Robot learning provides a promising alternative. Two well-established learning techniques are Programming by Demonstration (PbD) and Learning from Exploration (LfE). PbD and LfE are often combined to strengthen each other. PbD is used because it allows fast learning: with only a few demonstrations, robots are able to reproduce tasks with reasonable performance. After these demonstrations, LfE is used to improve the robot's task performance or to adjust this skills to changing environments. Robots often use continuous mappings between states and actions to represent a skill. Such mappings are called policies and are represented by function approximators. The shape of the policy is determined by the parameters. During learning the robot tries to find optimal parameters for the policy. As the complexity of the skill increases, the number of parameters required to accurately describe the policy for this skill also increases. As the number of parameters increases, the complexity of the solution space increases as well. It is most likely that the LfE algorithm requires more trials to converge for these complex search spaces than simpler search spaces, thus the LfE performance decreases as the complexity of the search space increases. In this thesis a novel multi-resolution policy representation is investigated. The method, called Tree-based policy representation, creates a multi-resolution model based on demonstration data. After this initialization, LfE can use the structure of the Multi-resolution policy to increase learning performance. The method is tested in multiple experimental scenarios. The Tree-based policy representation achieves better learning performance compared to conventional `flat' policy representations, when learning motions that clearly have a multi-resolution aspect. In other cases, the Tree-based movement representation performs equally well or worse compared to standard `flat' policy representations.BMDBioMechanical EngineeringMechanical, Maritime and Materials Engineerin
Comparison of older and newer generations of ActiGraph accelerometers with the normal filter and the low frequency extension
No full textabstract: Background
Many studies used the older ActiGraph (7164) for physical activity measurement, but this model has been replaced with newer ones (e.g., GT3X+). The assumption that new generation models are more accurate has been questioned, especially for measuring lower intensity levels. The low-frequency extension (LFE) increases the low-intensity sensitivity of newer models, but its comparability with older models is unknown. This study compared step counts and physical activity collected with the 7164 and GT3X + using the Normal Filter and the LFE (GT3X+N and GT3X+LFE, respectively).
Findings
Twenty-five adults wore 2 accelerometer models simultaneously for 3Âdays and were instructed to engage in typical behaviors. Average daily step counts and minutes per day in nonwear, sedentary, light, moderate, and vigorous activity were calculated. Repeated measures ANOVAs with post-hoc pairwise comparisons were used to compare mean values. Means for the GT3X+N and 7164 were significantly different in 4 of the 6 categories (p < .05). The GT3X+N showed 2041 fewer steps per day and more sedentary, less light, and less moderate than the 7164 (+25.6, -31.2, -2.9 mins/day, respectively). The GT3X+LFE showed non-significant differences in 5 of 6 categories but recorded significantly more steps (+3597 steps/day; p < .001) than the 7164.
Conclusion
Studies using the newer ActiGraphs should employ the LFE for greater sensitivity to lower intensity activity and more comparable activity results with studies using the older models. Newer generation ActiGraphs do not produce comparable step counts to the older generation devices with the Normal filter or the LFE.The electronic version of this article is the complete one and can be found online at: https://ijbnpa.biomedcentral.com/articles/10.1186/1479-5868-10-5
Author stance in doctoral dissertations of native and non-native speakers of English: a corpus-based study on epistemic adverbs
No full textOur study concentrates on the epistemic adverbs used in conveying author stance in academic English. The Contrastive Interlanguage Analysis (Granger, 1996) was run to three sets of corpora comprising doctoral dissertations written by native and non-native academic authors of English. Epistemic adverbs occurring in the dissertations were identified through a computer programme and their frequencies were separately computed for each corpus. Lastly, a log-likelihood test was administered to see whether there is a statistically significant difference across the groups in concern concerning the use of these adverbs.Nuestro estudio se centra en los adverbios epistémicos que se usan para indicar el punto de vista de un autor en inglés académico. El Contrastive Interlanguage Analysis (Granger, 1996) se aplica a tres grupos de corpus de tesis doctorales escritas en inglés por autores nativos y no nativos. Usando medios informáticos, se identificaron los adverbios.ESC
Intercultural elements in the short story Donnie, by the German speaking author Sherko Fatah
No full textEl presente artículo analiza en qué consisten y cómo se articulan los aspectos interculturales en Donnie (2002), el primer texto literario del escritor de habla alemana Sherko Fatah (1964). En concreto, estudia si se produce una relación dialógica entre las memorias culturales y las lenguas que en él aparecen como posible clave de su modelo literario, describiendo y explicando los principales elementos interculturales que conforman los pilares de su proyecto, así como las funciones que llevan a cabo, a través de la propuesta del germanista Carmine Chiellino, un autor de referencia en los estudios literarios interculturales en Alemania, y el concepto de ‘memoria cultural’ de los egiptólogos Aleida y Jan Assmann.This contribution analyses the first literary text of the author Sherko Fatah (b.1964), focusing on the presence of intercultural elements, the dialogical relation between the cultural memories and the languages that appear in the text as a possible key to his literary model. The article also describes and explains the main intercultural items that form the pillars of his project, as well as the role these items play based on the theoretical proposal of Carmine Chiellino, an expert in intercultural literary studies in Germany, and Jan and Aleida Assmann’s concept of cultural memory.17215716ESC
Evaluation of ActiGraph’s Low-Frequency Filter in Laboratory and Free-Living Environments
No full textThe ActiGraph (AG) is the most commonly used research-grade physical activity monitor. Although several investigators have examined the effects of the “low-frequency extension” (LFE) on step counts in the free-living environment, a direct comparison with a valid criterion method is lacking. We sought to determine the accuracy of the AG’s LFE to measure step counts during laboratory and free-living activities in two versions of the device (GT1M and GT3X). Methods: Twenty-four participants wore the StepWatch 3 and two versions of the AG, with the LFE turned on (GT1M-LFE and GT3X-LFE) and the LFE turned off (GT1M-N and GT3X-N), on different days. Direct observation of steps and the ankle-worn StepWatch 3 served as the criterion methods for the treadmill and free-living condition, respectively. All statistical analyses were performed on the percent difference between the devices as [(measured - actual)/actual]. Results: During treadmill walking, the GT1M-N and GT3X-N underestimated steps by approximately 60% at 40 m•min-1 (P\u3c 0.001) and by 31% at 54 m•min-1 (P \u3c 0.001). With the LFE turned on, this underestimation was reduced to 7% and 4% for the GT1M and GT3X, respectively. Under free-living conditions, both the GT1M-LFE and GT3X-LFE overestimated steps by approximately 32% (P \u3c 0.001) whereas the GT1M-N and GT3X-N steps were underestimated by 30% and 25%, respectively (P\u3c 0.001). Conclusions: Turning the LFE on lessens the underestimation of steps recorded at walking speeds \u3c54 m•min-1 for both the GT3X and GT1M. However, the increased sensitivity provided by the AG’s LFE results in overestimation of steps taken throughout the day, when compared with the criterion device. Meanwhile, failure to turn the LFE on results in an underestimation of steps taken throughout the day. [ABSTRACT FROM AUTHOR
Author stance in doctoral dissertations of native and non-native speakers of English: A corpus-based study on epistemic adverbs
No full textAcademic writing is not just about conveying an ideational ‘content’, it is also about the representation of the self (Hyland, 2002, p. 1092). It allows writers ‘to gain credibility by projecting an identity invested with the individual authority, displaying confidence in their evaluations and commitment to their ideas (Hyland, 2002, p. 1092). Our study concentrates on the epistemic adverbs used in conveying author stance in academic English. The Contrastive Interlanguage Analysis (Granger, 1996) was run to three sets of corpora comprising doctoral dissertations written by native and non-native academic authors of English. Epistemic adverbs occurring in the dissertations were identified through a computer programme and their frequencies were separately computed for each corpus. Lastly, a log-likelihood test was administered to see whether there is a statistically significant difference across the groups in concern concerning the use of these adverbs.DOI: 10.20420/rlfe.2015.001
Examining the effects of applying ActiGraph low-frequency extension feature to analyze the sleeping behaviours of preschool-aged children
No full textThis study compares sleep outcome measures obtained using normal- and low-frequency extension (LFE) settings (Actilife). Forty-two children (aged 3–6 years) were instructed to wear an ActiGraph GT3X+ accelerometer on their hip for 7 days, 24 h/day. Total sleep time (min), sleep efficiency (%), and number and cumulative length (min) of awakening were used to compare the settings. Results suggest that the LFE setting results in significant but relatively small reductions in the sleep metrics of children. Trial registration no.: clincialtrials.gov (ID no. NCT02223234)
Novelty
• LFE setting, available through ActiGraph, estimates a significantly reduced total sleep time and efficiency.The presentation of the authors' names and (or) special characters in the title of the pdf file of the accepted manuscript may differ slightly from what is displayed on the item page. The information in the pdf file of the accepted manuscript reflects the original submission by the author
World Englishes, English as a Lingua Franca and Lingua Franca English: Conceptualizing English Ownership and Use Beyond the NS Construct
No full textThis literature review explores the primary perspectives seeking to move beyond the Native Speaker（NS） as the preeminent cultural and linguistic target for language acquisition and use: 1） World Englishes（WE）, 2） English as a Lingua Franca（ELF）and 3） Lingua Franca English（LFE）. These perspectives seek to challenge the NS construct as a regime of truth（Foucault, 1980）both pragmatically and critically, in light of the adoption, transformation and adaptation of English in an ever-globalizing, postmodernistic world（Canagarajah, 2007）. In the review, the author examines the origins and nature of WE, ELF and LFE, highlighting their commonalities and differences in a critical fashion.departmental bulletin pape
ACTIGRAPH’S LOW-FREQUENCY EXTENSION FILTER FOR ESTIMATING WRIST-WORN PHYSICAL ACTIVITY IN OLDER ADULTS
No full textThis is a pre-copyedited, author-produced version of an article accepted for publication in Innovation in Aging following peer review. The version of record Hicks, Hilary J et al. “ACTIGRAPH’S LOW-FREQUENCY EXTENSION FILTER FOR ESTIMATING WRIST-WORN PHYSICAL ACTIVITY IN OLDER ADULTS.” Innovation in Aging vol. 3,Suppl 1 S520–S521. 8 Nov. 2019, doi:10.1093/geroni/igz038.1918 is available online at: https://doi.org/10.1093/geroni/igz038.1918.
This work is licensed under a Creative Commons Attribution 4.0 International License.Advancements in body-worn activity devices make them valuable for objective physical activity measurement. Research-grade monitors utilize software algorithms developed with younger populations using waist-worn devices. ActiGraph offers the low frequency extension (LFE) filter which reduces the movement threshold to capture low acceleration activity that is more common in older adults. It is unclear how this filter changes activity variable calculations in older adults. We investigated the effects of the LFE filter on wrist-worn activity estimates in this population. Participants were 21 older adults who wore the GT9X on their non-dominant wrist for 7 days in a free-living environment. Activity counts were estimated both with and without the LFE filter. Paired samples t-tests revealed that the LFE estimated significantly higher number of counts than non-LFE calculated counts per minute on all three axes (p < .001). Step count estimates were higher with (M = 20,780.09, SD = 5300.85) vs. without (M = 10,896.54, SD = 3489.45) the LFE filter, (t (20) = -22.21, p < .001). These differences have implications for calculations based on axis counts (e.g., Axis-1 calculated steps, intensity level classifications) that rely on waist-worn standards. For example, even without the filter, the GT9X calculated an average of 10,897 steps, which is likely an overestimate in this population. This suggests that axes-based variables should be interpreted with caution when generated with wrist-worn data, and future studies should aim to develop separate wrist and waist-worn standard estimates of these variables in older adult populations
Polysemy in specialized lexicon from Old English to Present-Day English
No full textThe main aim of this paper is to show the multiplicity of meanings given to the same word in specialized English lexicon from Old English to Present-Day English in order to provide the English language with linguistic economy and flexibility, thus increasing its vocabulary. The terms analysed are extracted from the OED, together with their date, author and work where they were first registered with the different meanings, and they mainly belong to Commerce, Law, Chemistry, Mathematics, Physics, Technology and Computing.ESCIERIH PLU
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