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Artykuły w czasopismach na temat "Within-task variability"
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Stark, J., C. Pons i O. Kurka. "Within-Task and Across-Task Variability in Agrammatic Narrative Production". Procedia - Social and Behavioral Sciences 61 (październik 2012): 255–56. http://dx.doi.org/10.1016/j.sbspro.2012.10.174.
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Musso, Mandi, Holly James Westervelt, Jeffrey D. Long, Erin Morgan, Steven Paul Woods, Megan M. Smith, Wenjing Lu i Jane S. Paulsen. "Intra-individual Variability in Prodromal Huntington Disease and Its Relationship to Genetic Burden". Journal of the International Neuropsychological Society 21, nr 1 (styczeń 2015): 8–21. http://dx.doi.org/10.1017/s1355617714001076.
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AbstractThe current study sought to examine the utility of intra-individual variability (IIV) in distinguishing participants with prodromal Huntington disease (HD) from nongene-expanded controls. IIV across 15 neuropsychological tasks and within-task IIV using a self-paced timing task were compared as a single measure of processing speed (Symbol Digit Modalities Test [SDMT]) in 693 gene-expanded and 191 nongene-expanded participants from the PREDICT-HD study. After adjusting for depressive symptoms and motor functioning, individuals estimated to be closest to HD diagnosis displayed higher levels of across- and within-task variability when compared to controls and those prodromal HD participants far from disease onset (FICV(3,877)=11.25; p<.0001; FPacedTiming(3,877)=22.89; p<.0001). When prodromal HD participants closest to HD diagnosis were compared to controls, Cohen’s d effect sizes were larger in magnitude for the within-task variability measure, paced timing (−1.01), and the SDMT (−0.79) and paced tapping coefficient of variation (CV) (−0.79) compared to the measures of across-task variability [CV (0.55); intra-individual standard deviation (0.26)]. Across-task variability may be a sensitive marker of cognitive decline in individuals with prodromal HD approaching disease onset. However, individual neuropsychological tasks, including a measure of within-task variability, produced larger effect sizes than an index of across-task IIV in this sample. (JINS, 2015, 21, 8–21)
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Gradin, Victoria, Viktoria-Eleni Gountouna, Gordon Waiter, Trevor S. Ahearn, David Brennan, Barrie Condon, Ian Marshall i in. "Between- and within-scanner variability in the CaliBrain study n-back cognitive task". Psychiatry Research: Neuroimaging 184, nr 2 (listopad 2010): 86–95. http://dx.doi.org/10.1016/j.pscychresns.2010.08.010.
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Malmberg, Lars-Erik, Wee H. T. Lim, Asko Tolvanen i Jari-Erik Nurmi. "Within-student variability in learning experiences, and teachers’ perceptions of students’ task-focus". Frontline Learning Research 4, nr 5 (19.12.2016): 62–82. http://dx.doi.org/10.14786/flr.v4i5.227.
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Jarus, Tal, Emily H. Wughalter i John G. Gianutsos. "Effects of Contextual Interference and Conditions of Movement Task on Acquisition, Retention, and Transfer of Motor Skills by Women". Perceptual and Motor Skills 84, nr 1 (luty 1997): 179–93. http://dx.doi.org/10.2466/pms.1997.84.1.179.
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This experiment was designed to investigate varying conditions of contextual interference within two different conditions of movement tasks during acquisition on the acquisition and retention of a computerized task and transfer to a functional skill. Performance of head movements was conducted under open- or closed-task conditions and with random or blocked schedules of practice. Analysis indicated that learning under the open-task condition resulted in better retention and transfer than the closed-task condition. It is suggested that increasing the within-trial variability in the open-task condition produced a contextual interference effect. In this regard, support for Battig's predictions is provided by the current findings in that the high variability present during the open-task condition was more beneficial for retention and transfer than the low variability present during the closed-task condition. Differences between random and blocked schedules of practice on the retention and transfer data were not statistically significant.
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Gaillard, Audrey, i Isabel Urdapilleta. "Sorting Food Labels and Describing Properties of Categories: Stability of Results between and within Subjects". Psychological Reports 109, nr 1 (sierpień 2011): 187–207. http://dx.doi.org/10.2466/10.13.22.28.pr0.109.4.187-207.
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The purpose of this research is to improve understanding of the consistency of the categorization process in cognitive psychology. To investigate the temporal stability of the categorization process between and within subjects, 100 participants ( M = 22.1 yr., SD = 2.1) were required to sort 65 food labels into groups and to explain their grouping. The sorting and property generation of food labels were compared by conducting two sessions (with a 15-day interval) to assess within-subject variability. Two groups of participants were compared to assess between-subjects variability. The results from the sorting task showed excellent stability between and within subjects. Conversely, the property generation task showed high variability. It is concluded that the tasks involved different types of knowledge. The sorting task appeared to generate good agreement and to involve more stable knowledge. The task of producing properties may involve other mechanisms. This paper discusses the results in light of cognitive and pragmatic theories.
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Miller, Suzanne Bonneau, i Katharine H. Odell. "Age-Related Intraindividual Performance Variability with Practice". International Journal of Aging and Human Development 65, nr 2 (wrzesień 2007): 97–120. http://dx.doi.org/10.2190/ag.65.2.a.
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Fluctuations in cognitive task performance in older individuals have been reported. To examine intraindividual variability as a function of practice, 34 younger and 34 older female participants, aged 20–30 years and 70–82 years, respectively, performed a reading span task 16 times over four sessions. Each individual's recall accuracy was analyzed over the practice trials. It was found that intraindividual variability occurred more frequently in older than younger individuals, and that fluctuations were more frequent in mid to later trials of practice. These findings were interpreted within a resource theory framework as evidence for age-related inefficient cognitive processing with practice.
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Phillips, Christine B., Jerri D. Edwards, Ross Andel i Marcus Kilpatrick. "Daily Physical Activity and Cognitive Function Variability in Older Adults". Journal of Aging and Physical Activity 24, nr 2 (kwiecień 2016): 256–67. http://dx.doi.org/10.1123/japa.2014-0222.
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Physical activity (PA) is believed to preserve cognitive function in older adulthood, though little is known about these relationships within the context of daily life. The present microlongitudinal pilot study explored within- and between-person relationships between daily PA and cognitive function and also examined within-person effect sizes in a sample of community-dwelling older adults. Fifty-one healthy participants (mean age = 70.1 years) wore an accelerometer and completed a cognitive assessment battery for five days. There were no significant associations between cognitive task performance and participants’ daily or average PA over the study period. Effect size estimates indicated that PA explained 0–24% of within-person variability in cognitive function, depending on cognitive task and PA dose. Results indicate that PA may have near-term cognitive effects and should be explored as a possible strategy to enhance older adults’ ability to perform cognitively complex activities within the context of daily living.
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van Dieën, Jaap H., Joris J. M. Dekkers, Vincent Groen, Huub M. Toussaint i Onno G. Meijer. "Within-Subject Variability in Low Back Load in a Repetitively Performed, Mildly Constrained Lifting Task". Spine 26, nr 16 (sierpień 2001): 1799–804. http://dx.doi.org/10.1097/00007632-200108150-00016.
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Mathiassen, Svend Erik, Therése Möller i Mikael Forsman. "Variability in mechanical exposure within and between individuals performing a highly constrained industrial work task". Ergonomics 46, nr 8 (czerwiec 2003): 800–824. http://dx.doi.org/10.1080/0014013031000090125.
Pełny tekst źródłaRozprawy doktorskie na temat "Within-task variability"
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Nelson, Jeffrey. "Executive functioning and the adaptation to novelty". University of Western Australia. School of Psychology, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0157.
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[Truncated thesis] This thesis is concerned with executive functioning in two different but related ways. The first is as an information processing construct in cognitive psychology. There are many different conceptualisations of the information processing basis of executive functioning but this thesis will pursue the notion that executive functioning is best thought of as adaptation to novelty. In the thesis, this will be operationalised using performance indices (principally reaction time) from a number of information processing tasks. These tasks have typically been used in the literature to index either executive functioning or speed of information processing. Both kinds of tasks are used to tackle the second concern of this thesis, namely, how executive functioning is measured. The data analytic techniques developed in this thesis are based on the hypothesis that executive functioning is the process or processes involved in resolving task novelty and consequently measurement will be enhanced through an analysis of performance changes within tasks as the task changes from novel to familiar. The analysis methods will be based largely on the computation of coefficient of variation of reaction time in successive performance windows across the information processing tasks. An elderly sample was chosen for this thesis because of a history of research that has attempted to determine whether cognitive deficits in the elderly are the consequence of the slowing of information processing speed or to impairment in executive functioning. ... The analysis was driven by the hypothesis that a significant shift in the coefficient of variation would mark a transition from novelty to familiarity in task performance and hence from executive to non-executive phases. Three methods were applied to individual performance curves to determine the point at which for each task this transition occurred. Using criterion measures of variability to separate the task data into two stages, analyses showed, contrary to the hypothesis, that later task performance was more highly associated with executive functioning than in initial task performance. The fourth stage of analysis (Chapter 7) applied confirmatory factor analysis to the newly-formed pre- and post transition data. Evidence was found that the magnitude of the contributions of EF across the pre- and post-criterion phases was stable, failing to support the hypothesis. Finally, structural equation modelling was used to examine how age and intelligence in this elderly sample exerts its influence on task performance and whether EF or IPS was the primary cause of age-related cognitive decline. The results showed that the age and intelligence effects on performance were mediated by the requirement to adapt to novelty. Although there was limited evidence to claim that EF is the primary cause of age-related cognitive decline, ageing effects were only apparent when the participants were adapting to novelty. The thesis concludes that there is some support for the hypothesis that executive functioning is best thought of as the processes underpinning adaptation to novelty. While not a panacea, the analytic techniques developed show promise for future research.
Książki na temat "Within-task variability"
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Bagdasaryan, Vardan. Leadership. ru: INFRA-M Academic Publishing LLC., 2021. http://dx.doi.org/10.12737/1086964.
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The study of the course "Leadership" is associated with an increasing demand for the formation and disclosure of human leadership potentials. The presented textbook allows you to carry out this work in a targeted way. It summarizes and systematizes the world experience in the development of the theory and practice of leadership, discusses the classification of types of leaders, issues of practical use in leadership scenarios of personal qualities of a person, and offers a methodology for developing team strategies and team building. The distinctive features of the proposed program are its adaptability to the socio-cultural context of Russian society and its strong connection with the task of training the future generation of leaders in the interests of the Russian state. Each of the sections of the textbook is accompanied by practical tasks, the solution of which develops the skills of self-knowledge of a person in the perspective of developing leadership potentials and understanding the variability of leadership strategies. It is focused primarily on the preparation of bachelors studying in pedagogical areas of training, but it can also serve as a basic source for training in the course "Leadership" within the framework of a bachelor's degree in the humanities and the direction of social sciences.
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Scott, Brent A., Fadel K. Matta i Joel Koopman. Within-Person Approaches to the Study of Organizational Citizenship Behaviors: Antecedents, Consequences, and Boundary Conditions. Redaktorzy Philip M. Podsakoff, Scott B. Mackenzie i Nathan P. Podsakoff. Oxford University Press, 2016. http://dx.doi.org/10.1093/oxfordhb/9780190219000.013.17.
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This chapter provides a review of the nascent (but growing) literature on organizational citizenship behavior (OCB) at the within-person level of analysis. We organize our review of the existing literature chronologically, discussing antecedents and consequences of within-person fluctuations in OCB. After providing a narrative review of the literature, we provide a quantitative summary of the literature via meta-analysis, summarizing the within-person relationships between OCB and its most common within-person correlates (i.e., positive affect, negative affect, job satisfaction, stressors, strain, and task performance). Looking to the future of OCB at the within-person level of analysis, we suggest that researchers can contribute to the domain by tailoring the measurement of OCB to the within-person level of analysis, better illuminating the causal direction between OCB and affect, clarifying the relationship between OCB and counterproductive work behavior at the within-person level, expanding the “dark side” of within-person OCB, exploring between-person differences in within-person OCB variability, and incorporating new theories.
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Bindemann, Markus, red. Forensic Face Matching. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780198837749.001.0001.
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Person identification at passport control, at borders, in police investigations, and in criminal trials relies critically on the identity verification of people via image-to-image or person-to-image comparison. While this task is known as ‘facial image comparison’ in forensic settings, it has been studied as ‘unfamiliar face matching’ in cognitive science. This book brings together expertise from practitioners, and academics in psychology and law, to draw together what is currently known about these tasks. It explains the problem of identity impostors and how within-person variability and between-person similarity, due to factors such as image quality, lighting direction, and view, affect identification. A framework to develop a cognitive theory of face matching is offered. The face-matching abilities of untrained lay observers, facial reviewers, facial examiners, and super-recognizers are analysed and contrasted. Individual differences between observers, learning and training for face recognition and face matching, and personnel selection are reviewed. The admissibility criteria of evidence from face matching in legal settings are considered, focusing on aspects such as the requirement of relevance, the prohibition on evidence of opinion, and reliability. Key concepts relevant to automatic face recognition algorithms at airports and in police investigations are explained, such as deep convolutional neural networks, biometrics, and human–computer interaction. Finally, new security threats in the form of hyper-realistic mask disguises are considered, including the impact these have on person identification in applied and laboratory settings.
Części książek na temat "Within-task variability"
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Ali, Jauhar, Mahender Anumalla, Varunseelan Murugaiyan i Zhikang Li. "Green Super Rice (GSR) Traits: Breeding and Genetics for Multiple Biotic and Abiotic Stress Tolerance in Rice". W Rice Improvement, 59–97. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-66530-2_3.
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AbstractThe frequent fluctuations in global climate variability (GCV), decreases in farmland and irrigation water, soil degradation and erosion, and increasing fertilizer costs are the significant factors in declining rice productivity, mainly in Asia and Africa. Under GCV scenarios, it is a challenging task to meet the rice food demand of the growing population. Identifying green traits (tolerance of biotic and abiotic stresses, nutrient-use efficiency, and nutritional grain quality) and stacking them in high-yielding elite genetic backgrounds is one promising approach to increase rice productivity. To this end, the Green Super Rice (GSR) breeding strategy helps to pool multi-stress-tolerance traits by stringent selection processes and to develop superior GSR cultivars within a short span of 4–5 years. In the crossing and selection process of GSR breeding, selective introgression lines (SILs) derived from sets of early backcross BC1F2 bulk populations through both target traits and non-target traits were selected. Genotyping of SILs with high-density SNP markers leads to the identification of a large number of SNP markers linked with the target green traits. The identified SILs with superior trait combinations were used for designed QTL pyramiding to combine different target green traits. The GSR breeding strategy also focused on nutrient- and water-use efficiency besides environment-friendly green features primarily to increase grain yield and income returns for resource-poor farmers. In this chapter, we have highlighted the GSR breeding strategy and QTL introgression of green traits in rice. This breeding strategy has successfully dissected many complex traits and also released several multi-stress-tolerant varieties with high grain yield and productivity in the target regions of Asia and Africa.
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Siegler, Robert S. "Cognitive Variability: The Ubiquity of Multiplicity". W Emerging Minds. Oxford University Press, 1996. http://dx.doi.org/10.1093/oso/9780195077872.003.0006.
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No one doubts that immense variability exists at the neural level. Even when the identical stimulus is presented repeatedly within a single experimental session, the response of an individual neuron varies from trial to trial. Similarly, with lowlevel cognitive processes such as association, there is no disagreement concerning the existence of competing units. Models of associative memory, both symbolic (e.g., Gillilund & Shiffrin, 1984) and subsymbolic (e.g., Seidenberg & McClelland, 1990), are predicated on the assumptions that stimuli have multiple associations and that these varying associations influence the way in which we remember. Higher level cognition, however, has been treated differently. Many models are universalist: Everyone is depicted as proceeding in the same way when relevant stimuli are presented. Other models are comparative; they hypothesize different ways of thinking among groups defined on the basis of such characteristics as age, expertise, or aptitudes, but hypothesize a single consistent kind of reasoning within each group. Thus, 8-year-olds might be depicted as performing in one way and 5-year-olds in another, experts in one way and novices in another, people with high spatial ability in one way and those with low spatial ability in another, and so on. The finest differentiations that are typically made within these comparative approaches examine individual differences within people of a single age; for example, reflective 8-year-olds are described as taking a long time but answering accurately on the Matching Familar Figures Test, and impulsive 8-year-olds are described as answering more quickly but less accurately (Kogan, 1983). The main purpose of this chapter is to summarize the rapidly growing body of research suggesting that variability is actually a pervasive reality in high-level, as well as low-level, cognition. To place this work in context, however, it seems useful first to briefly consider some prominent examples of universalist and comparative models of cognition and then to consider why they might be proposed and widely accepted even if thinking is far more variable than they depict it as being. A great deal of cognitive research has been devoted to identifying the processing approach that people use on a particular task. This universalist approach has led to many influential models and theories.
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Mikołajewska, Emilia, i Dariusz Mikołajewski. "Models of Cooperation between Medical Specialists and Biomedical Engineers in Neuroprosthetics". W Healthcare Ethics and Training, 1473–89. IGI Global, 2017. http://dx.doi.org/10.4018/978-1-5225-2237-9.ch070.
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The development of novel technologies associated with neuroprosthetics and their clinical applications needs interdisciplinary knowledge, including not only medical sciences, but IT, biomedical engineering, biocybernetics, and robotics. The variability of possible neurological deficits, interventions, and even scales—from nanotechnology up to rehabilitation robots and brain-computer-interface controlled exoskeletons as whole-body neuroprostheses—makes this task very difficult. Current models of education and cooperation within interdisciplinary therapeutic teams only concern medical specialists. This chapter tries to answer the question, how can biomedical engineers be incorporated into research and clinical practice in neuroprosthetics considering the various aforementioned factors, necessary changes in educational processes, ethical issues, and associated organizational problems?
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Komendziński, Tomasz, Joanna Dreszer-Drogorób, Emilia Mikołajewska, Dariusz Mikołajewski i Bibianna Bałaj. "Interdisciplinary Education for Research and Everyday Clinical Practice". W Advances in Medical Education, Research, and Ethics, 78–110. IGI Global, 2016. http://dx.doi.org/10.4018/978-1-4666-9658-7.ch004.
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Teamwork, interprofessional practice and learning are integral to current interdisciplinary research and health care – such approach can maximize professional resources and optimize outcomes. The development of modern technologies associated with medical sciences, and the variability of possible neurological deficits, interventions, and even scales makes this task very difficult. The key problem is regarded successful transition of students to competent work-ready professionals. Current models of education and cooperation within interdisciplinary teams may be not enough flexible. This chapter, based on own experiences from InteRDoCTor project, tries to answer the question: how shape interdisciplinary education and how their results may be wider incorporated into research and clinical practice?
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Bindemann, Markus, i A. Mike Burton. "Steps Towards a Cognitive Theory of Unfamiliar Face Matching". W Forensic Face Matching, 38–61. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780198837749.003.0003.
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The visual comparison of unfamiliar faces—or ‘face matching’—is utilized widely for person identification in applied settings and has generated substantial research interest in psychology, but a cognitive theory to explain how observers perform this task does not exist. This chapter outlines issues of importance to support the development of a cognitive account of unfamiliar face matching. Characteristics of the face, such as within-person variability and between-person similarity in appearance, are considered as the visual input upon which identification must build. The cognitive mechanisms that observers may bring to bear on faces during identity comparison are analysed, focusing on attention, perception, evaluation, and decision processes, including sources of individual differences at each of these stages. Finally, the role of different experimental and occupational contexts in understanding face matching and for optimizing theory development is discussed.
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Siegler, Robert S. "Strategic Development: Trudging up the Staircase or Swimming with the Tide?" W Emerging Minds. Oxford University Press, 1996. http://dx.doi.org/10.1093/oso/9780195077872.003.0007.
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As described in the previous chapter, children’s thinking is highly variable. The present chapter focuses on implications of this variability for understanding development. Thinking about a pair of visual metaphors may help facilitate recognition of these implications. The first, which I believe underlies most depictions of development, is the staircase metaphor. The second, which I believe offers a superior alternative, is the overlapping waves metaphor. Cognitive developmentalists have often phrased their models in terms that suggest that children of a given age think about a given task in a single way. W-year-olds are said to have a particular mental structure, a particular processing limit, a particular theory, strategy, or rule that gives rise to a single type of behavior. Change involves a substitution of one mental entity (and accompanying behavior) for another. The basic conceptualization that seems to underlie these models is aptly captured in the title of Robbie Case’s (1992) recent book The Mind’s Staircase. The visual metaphor that this title evokes is, I believe, central to most cognitive-developmental treatments of change: Children are depicted as thinking in a given way for an extended period of time (a tread on the staircase); then their thinking undergoes a sudden, vertical shift (a riser on the staircase); then they think in a different, higher way for another extended period of time (the next tread); and so on. This view of development is most closely identified with Piagetian and neo-Piagetian approaches, such as those of Piaget and Case. Thus, as shown in Figure 4.1, we see development depicted within Piaget’s theory as involving sensorimotor activities from birth to about 2 years; preoperational thinking from 2 to 7 years; concrete operational thinking from 7 to 12 years; and formal operational thinking from 12 years onward. Within Case’s theory, we see thinking depicted as advancing from the sensorimotor level between birth and 18 months, to the relational level from 18 months to 5 years, to the dimensional level between 5 and 11 years, and to the formal level at age 11 and beyond. Although this view of development is associated with the Piagetian and neo-Piagetian traditions, it is far from unique to them.
Streszczenia konferencji na temat "Within-task variability"
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Cloutier, Aimee, Jared Gragg, Jingzhou Yang i Fisseha Alemayehu. "Sensitivity Analysis of Achieving a Reach Task within a Vehicle Considering Joint Angle Variability". W SAE 2012 World Congress & Exhibition. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 2012. http://dx.doi.org/10.4271/2012-01-0058.
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Bonacuse, Peter J., Subodh Mital i Robert Goldberg. "Characterization of the As Manufactured Variability in a CVI SiC/SiC Woven Composite". W ASME 2011 Turbo Expo: Turbine Technical Conference and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/gt2011-45890.
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The microstructure of a 2D woven ceramic matrix composite displays significant variability and irregularity. For example, a chemical vapor infiltrated (CVI) SiC/SiC composite exhibits significant amount of porosity arranged in irregular patterns. Furthermore, the fiber tows within a ply frequently have irregular shape and spacing, and the stacked plies are often misaligned and nested within each other. The goal of an ongoing project at NASA Glenn is to investigate the effects of the complex microstructure and its variability on the properties and the durability of the material. One key requirement for this effort is the development of methods to characterize the distribution in as-fabricated ceramic matrix composite (CMC) microstructures with the objective of correlating microstructural distribution parameters with mechanical performance. An initial task in this effort was to perform quantitative image analysis of polished cross sections of CVI SiC/SiC composite specimens. This analysis provided sample distributions of various microstructural composite features, including: inter-tow pore sizes and shapes, transverse sectioned tow sizes and shapes, and within ply tow spacing. This information can then be used to quantify the effect of extreme values of these features on the local stress state with the goal of determining the likelihood of matrix cracking at a given external load.
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Rajagopalan, Sanjay, i Mark R. Cutkosky. "Optimal Pose Selection for In-Situ Fabrication of Planar Mechanisms". W ASME 1999 Design Engineering Technical Conferences. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/detc99/dfm-8958.
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Abstract Solid Freeform Fabrication (SFF) techniques allow the in-situ fabrication of fully-assembled devices with mating/fitting parts. Recently, this technique of fabrication has been found to be useful for building integrated mechanisms in robotics, and a wide array of other similar applications are anticipated. An interesting issue that arises during the fabrication of such mechanisms is the determination of an optimal pose in which the mechanism should be built. For example, should the mechanism be built in a folded or stretched-out position? In conventional manufacturing these issues do not arise, as each individual link is typically manufactured separately and then the pieces are brought together during assembly. In this paper, we address the issue of finding a preferred (or optimal) pose for in-situ fabrication of planar mechanisms. There are many factors (e.g. achievable tolerances, non-interference, workspace size limitations, thermal considerations etc.) which can determine the suitability of a candidate build pose so that pre-specified task requirements are met. We limit our analysis to finding the optimal build configuration given achievable (in general, non-homogeneous, anisotropic) accuracy on joint position. For this treatment, we also make the simplifying assumption that the task requirements can be best satisfied by minimizing variability of link-lengths. Alternate task requirements, for example, maintaining end-point accuracy within a tolerance region, are being considered as part of ongoing work. We cast the problem of minimizing variability in link length as that of determining the relative position of two location tolerance regions for which the difference between their extremal distances is at a minimum (i.e., as they undergo constrained relative motion in the Euclidean plane). The method is similar to computational geometry techniques that have been developed in pattern matching and robot motion planning, with some important differences. We present some example mechanisms and their optimal pose under given workspace configurations.
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Claesson, Anders, Bjo¨rn Rosvall i Hans Johannesson. "Capturing Design Knowledge of Robust Designs Using Configurable Components". W ASME 2005 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2005. http://dx.doi.org/10.1115/detc2005-85364.
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Development of complex, platform-based, and variant-rich products within the automotive industry is in many respects a challenging task. The competitive pressure within the industry requires more and more collaborative development and utilization of systems and components not only within, but also across, product platforms. In such an environment the ability to effectively and efficiently deal with how variability is achieved is an important issue. Many approaches to deal with configuration issues have been subject to extensive research and exploration. In the research presented here the basic idea is to merge influences from established design tools and methods with concepts from research on configuration tasks as well as from product description approaches used within the industry. The presented work has an exploratory nature that aims at increased understanding of the mechanisms, methodology and value of the application of the configurable component concept as a development support tool during platform-based vehicle development. The work presented here has been performed in parallel with a feasibility study for a vehicle cock-pit family. The study aims at investigating prerequisites for enabling a cock-pit solution to be shared as a common solution in several vehicle platforms as well as within each of the platforms. The paper contributes to the understanding of how configurable components can improve the definition and maintenance of design variants and facilitate reuse of these design solutions through the captured trail of design rationale that is achieved through the systematic use of the component definitions.
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Komeilizadeh, Koushiar, Mohsen Asghari, Juho-Antti Junno i Mohamad Parnianpour. "Monte Carlo Simulation of Spine Geometry From T12 to Sacrum in Males". W ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis. ASMEDC, 2010. http://dx.doi.org/10.1115/esda2010-25254.
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In biomechanical modeling of spine, the prediction of spinal loading during occupational activities is crucial in assessment of the risk of low back pain and injury of spine. Current biomechanical models are based on the average data. Hence, they are unable to predict the effects of the observed natural anatomical variations on muscles moment arms and lines of action, while these variations ultimately influence the required muscular forces for balancing the external moments of any given task. In this work, a methodology based on the Monte Carlo technique has been developed to simulate spine geometry from T12 to S1 vertebrae for males. The lordosis of the assembled spine ranged between 21° to 63° with an average equal to 42.2°, which is within the reported values in the literature. Obtained data could be used as an input to equilibrium/stability based biomechanical spine models to assess the contribution of different geometry. This model is intended to merge with our stochastic spine model of spine to test the effects of various sources of variability on spinal loadings and its risk of failure.
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Alexandratos, Spyridon A., Robert C. Wimpory, Tung-Lik Lee, Padraig Mac Ardghail, Sean B. Leen i Noel P. O’Dowd. "Comparison of Residual Stress Measurements on Single Bead-on-Plate Welds of a Martensitic Steel Using Neutron Diffraction". W ASME 2020 Pressure Vessels & Piping Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/pvp2020-21776.
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Abstract During the welding process, a material is subjected to thermal cycles with rapid heating and cooling rates resulting in residual stress in the weld and the base metal. These residual stress may affect the mechanical performance leading to premature failure of components. Therefore, it is critical to have a detailed knowledge of the residual stress distribution in the weld region as well as in the vicinity in order to predict the service life of components. Due to the high neutron penetration power, neutron diffraction is one of the most useful techniques for nondestructive evaluation of residual stress in welded regions within the bulk. In this paper, neutron diffraction was used to investigate the residual stress distribution within three single bead-on-plate welds of P91 martensitic steel. Residual stress measurements were performed at different neutron diffraction instruments and different methodology of stress determination was applied. Measurements were carried out at the diffractometers Engin-X (ISIS Neutron Source, Rutherford Appleton Laboratory), E3 (BER-II, Helmholtz-Zentrum Berlin) and SALSA (Institut Laue-Langevin). The results of the measurements presented here, were used to determine the variability of the three instruments and compare the effect of different welding parameters on residual stress. The residual stress measurements were also compared with the respective results of the Task Group 1 (TG1) of the European Network on Neutron Techniques standardization for structural integrity (NET).
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Ansari, Ajmal I. "Post Extrusion Cooling of Multilayer Polymer Sheet on Chilled Rolls". W ASME 2005 Summer Heat Transfer Conference collocated with the ASME 2005 Pacific Rim Technical Conference and Exhibition on Integration and Packaging of MEMS, NEMS, and Electronic Systems. ASMEDC, 2005. http://dx.doi.org/10.1115/ht2005-72459.
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To meet the stringent emission and environmental regulations, polymer sheet with as many as six layers is required for thermoformed fuel tanks used in the automotive industry. The 10 mm to 12 mm thick sheet is made using an extrusion process. Typically each polymer layer has its own hopper, screw, barrel, nozzle and extruder. During manufacturing, polymer layers are fused together within the tool and the multilayer polymer sheet leaves the extruder in a viscoelastic state. The multilayer sheet is initially cooled by passing it over chilled rolls. The final cooling of the sheet is done via natural convection to the ambient air while the sheet is transported to the cutting station at the end of the line. The cooling of the sheet on the chilled and polished rolls has a direct influence on the quality of the sheet as well as the scrap. The conductive heat transfer is primarily responsible for the cooling while the sheet is on the chilled roll. It is desired to have the smooth sheet exterior surfaces with constant thickness of each polymer layer in the cross section. Due to the numerous materials in the cross section, and associated variability of material properties, it becomes a challenging task to meet these requirements. This paper discusses the problem of the smoothness of the exterior surfaces of the extruded sheet. The “dimpled” or “orange peel” surface finish is observed to be linked to the cooling of the sheet on the chilled rolls. Experimental data and simulation results are presented that relate the formation of dimples to the local cooling rate. The variability of thermal contact resistance between the sheet surface and the chill rolls also appear to be another variable that contributes to the dimpled surface.
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Wilkin, Tim, Yakov Frayman i Bernard Rolfe. "Adaptive Control of the Closed Loop Behaviour of Manufacturing Processes". W ASME 8th Biennial Conference on Engineering Systems Design and Analysis. ASMEDC, 2006. http://dx.doi.org/10.1115/esda2006-95444.
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An open problem in manufacturing control is the design of controllers with guaranteed closed loop performance on plants subject to unmeasurable disturbances and changing dynamics. Existing methods for Adaptive Control of these plants typically rely on system identification techniques, which lead to a multi-objective optimisation task that offers no explicit guarantee regarding the stability of the closed loop system or the quality of its output. Robust Control design guarantees stability in the presence of unmeasured disturbances, although at the expense of sub-optimal control performance. We propose a control architecture and methodology for online adaptation of the process behavior that does not require explicit identification of the plant or disturbance dynamics. An arbitrary function approximator is used for control of the plant and the closed loop behaviour of this coupled system is adapted to that of a generic performance target. No exogenous signal is required for excitation of the adaptation, which instead used the inherent variability in the plant output. The use of a closed loop performance target for adaptation is practical, simple to implement and does not require a knowledge of either the plant dynamics or the disturbances acting on the process, since the controller is only concerned with maintaining transient process behavior within acceptable bounds. The resulting controller is capable of achieving a specified closed loop performance in the presence of unmeasurable, bounded disturbances, making the proposed scheme a viable candidate for disturbance rejection tasks.
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Bianchi, Gian Marco, Piero Pelloni, Giovanni Osbat, Marco Parotto, Rita Di Gioia, Stefania Falfari i Federico Brusiani. "The Role of Simulation in the Development of a Fast-Actuation Solenoid C.R. Injection System". W ASME 2004 Internal Combustion Engine Division Fall Technical Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/icef2004-0847.
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Upcoming Euro 4 and Euro 5 emission standards are increasing efforts on injection system developments in order to improve mixture quality and combustion efficiency. The target features of advanced injection system are related to their capability of operating multiple injection with a precise control of amount of fuel injected, low cycle-by-cycle variability and life drift, within flexible strategies. In order to accomplish this task, performance must be optimised since injection system concept development by acting on. The extensive use of numerical approach has been identified as a necessary integration to experiments in order to put on the market high quality injection system accomplishing strict engine control strategies. The modelling approach allows focusing the experimental campaign only on critical issues saving time and costs, furthermore it is possible to deeply understand inner phenomena that cannot be measured. The lump/ID model of the whole system built into the AMESim® code was presented in previous works: particular attention was devoted in the simulation of the electromagnetic circuits, actual fluid-dynamic forces acting on needle surfaces and discharge coefficients, evaluated by means 3D-CFD simulations. In order to assess new injection system dynamic response under multiple injection strategies reproducing actual engine operating conditions it is necessary to find to proper model settings. In this work the integration between the injector and the system model, which comprehends the pump, the pressure regulator, the rail and the connecting-pipes, will be presented. For reproducing the dynamic response of he whole system will be followed a step-by-step approach in order to prevent modelling inaccuracies. Firstly will be presented the linear analysis results performed in order to find injection system own natural frequencies. Secondly based on linear analysis results will be found proper injection system model settings for predicting dynamic response to external excitations, such as pump perturbations, pressure regulator dynamics and injection pulses. Thirdly experimental results in terms of instantaneous flow rate and integrated injected volume for different operating conditions will be presented in order to highlight the capability of the modelling methodology in addressing the new injection system design.