188,304 research outputs found
When gait isn't straight forward: how do you assess the ability to turn?
No full textFor people with Parkinson’s Disease (PD), difficulty
turning is a notorious cause of freezing and falls (Bloem
et al, 2001; Stack and Ashburn, 1999; Nieuwboer et al,
1998; Yekutiel, 1993; Giladi et al, 1992) and may lead
to a physiotherapy referral. What do therapists record
when turning is assessed informally, perhaps during a
standard mobility test? How do their findings guide
them? Turning is poorly understood in comparison
with straight forward gait:
• Studies have been small, with young, healthy
participants
• ‘Step Count’ and ‘Turn Time’ have dominated the
literature
• Unsubstantiated claims have been made about
‘normal’ turning
• Few existing measures have been validated
• Laboratory-based protocols are unsuitable for use
clinically or in PD research.
A new measure, the video-based Standing Start 180º
Turn Test (SS-180), has recently been developed at the
University of Southampton (Stack, 2003) and a paper
submitted to Physiotherapy detailing its design, validation
against a laboratory-based ‘gold standard’ and
initial reliability. The test is currently being used in a
number of studies. The purpose of this article is to raise
awareness of the SS-180 and to encourage consideration
of the issues associated with difficulty turning from
the clinical and research perspectives
Design improvement of circular molten carbonate fuel cell stack through CFD Analysis
Get PDFMolten carbonate fuel cell (MCFC) is a promising technology for distributed power generation. The core of an MCFC power generation unit is the stack, where various fuel cells are connected together in series and parallel in order to obtain the desired voltage and power. Stack geometry and configuration are major engineering topics, as inhomogeneous temperature or mass fractions cause inefficient performances of the fuel cells, as efficiency and power smaller than the expected and shorter lifetime. A detailed model is a useful tool to improve stack performances, through design improvements. In this paper, a 3D model of a stack composed of 15 circular MCFC, considering heat, mass and current transfer as well as chemical and electrochemical reactions is presented. The model validation is conducted using some preliminary experimental data obtained for an MCFC stack developed in the Fabbricazioni Nucleari laboratories. These results are examined in order to improve the stack configuration. It is shown that power density may be increased of about 20% through double side feeding. In addition, the average temperature gradients in the axial direction are reduced of more than 70%. Significant reductions in the temperature gradients, especially in transversal direction, can be achieved by adjusting the mass flow rate of cathodic gas supplied to the various cell
Numerical computation for parallel plate thermoacoustic heat exchangers in standing wave oscillatory flow
Get PDFA simplified computational method for studying the heat transfer characteristics of parallel plate thermoacoustic heat exchangers is presented. The model integrates the thermoacoustic equations of the standard linear theory into an energy balance-based numerical calculus scheme. Details of the time-averaged temperature and heat flux density distributions within a representative domain of the heat exchangers
and adjoining stack are given. The effect of operation conditions and geometrical parameters on the heat exchanger performance is investigated and main conclusions relevant for HX design are drawn as far as fin length, fin spacing, blockage ratio, gas and secondary fluid-side heat transfer coefficients are concerned. Most relevant is that
the fin length and spacing affect in conjunction the heat exchanger behaviour and have to be simultaneously optimized to minimize thermal losses localized at the HX-stack
junctions. Model predictions fit experimental data found in literature within 36% and 49% respectively at moderate and high acoustic Reynolds numbers
On Multi-stack Visibly Pushdown Languages
No full textWe contribute to the theory of formal languages of visibly multistack pushdown automata (MVPA). First, we show closure under the main operations and decidability of the main decision problems for the class of MVPA restricted to computations where a symbol can be popped out of a stack S only if it was pushed within the last k contexts of S, for a given k (in a context only one stack can be pushed or popped). In particular, this class turns out to be determinizable. Second, we show the closure under complement of the class of languages accepted by ordered MVPA (where the limitation is that a stack can be popped only if all the lower indexed stacks are empty). This gains decidability of universality, inclusion and equivalence for this class. As a further contribution, we compare the classes of languages accepted by different models of MVPA
Adaptive Selbstlernaufgaben mit STACK
No full text<p>Die Beschäftigung mit Übungsaufgaben ist das wichtigste Lerninstrument für die Mathematik. An der Ruhr-Universität Bochum werden fächerübergreifend Studierenden zur eigenverantwortlichen Vor- und Nachbereitung digitale Mathematikaufgaben in einem eLearning-Kurs zum Selbststudium angeboten. Diese nutzen intensiv die Randomisierungs- und die differenzierten Feedback-Möglichkeiten des Aufgabentyps STACK. Erste Aufgaben wurden nun durch adaptive Aufgabenstellungen, die auch Zwischenschritte ermöglichen, ergänzt.</p>
Movement strategies used during fall-related activities by repeat fallers and nonrepeat fallers with Parkinson's Disease (PD) (abstract of paper presented at Society for Research in Rehabilitation, Manchester 2001)
No full textMovement strategies used during fall related activities by repeat fallers and nonrepeat fallers with Parkinson's disease (PD) E Stack, A Ashburn and K JuppBackground: Information about the movement strategies deployed by repeat fallers (RFs) during fall-related activities is limited. The aims of this study were to describe how people with PD naturally turn and reach and compare the movement strategies of RFs with those of nonrepeat fallers (NRFs).Method: Independently mobile people with PD living in the community were recruited through GPs. Their disease severity, self-assessed disability and fall history was assessed at home. How subjects turned, reached high and reached low whilst making a cup of tea was video-recorded and rated blind using a validated, reliable checklist. Results: Seventy-five subjects (48 men), median age 73 years and median Hoehn and Yahr grade III were recruited. Forty-three subjects were RFs: they had greater disease severity and self-assessed disability than NRFs. Falls reported had occurred most frequently when walking (41%) or turning (17%). When turning, forwards stepping (33%) or sideways stepping (32%) movements were common, a median of six steps was taken, 88% demonstrated reduced heel strike and 25% used support. When reaching, 75% of subjects used support, 82% aligned forwards and 69% stood with their feet parallel. RFs and NRFs moved in similar ways, but RFs had a significantly smaller base width between their feet prior to moving (p < 0.001). Increased disease severity was linked with a high number of turning steps and observed instability.Conclusion: Surprisingly, the RFs were not distinguishable from NRFs by the way they moved during common fall-related activities. Rather, the small base area and apparent instability during functional activity should be targeted for intervention
Algorithmic Debugging of Real-World Haskell Programs: Deriving Dependencies from the Cost Centre Stack
Get PDFExisting algorithmic debuggers for Haskell require a transformation of all modules in a program, even libraries that the user does not want to debug and which may use language features not supported by the debugger. This is a pity, because a promising ap- proach to debugging is therefore not applicable to many real-world programs. We use the cost centre stack from the Glasgow Haskell Compiler profiling environment together with runtime value observations as provided by the Haskell Object Observation Debugger (HOOD) to collect enough information for algorithmic debugging. Program annotations are in suspected modules only. With this technique algorithmic debugging is applicable to a much larger set of Haskell programs. This demonstrates that for functional languages in general a simple stack trace extension is useful to support tasks such as profiling and debugging
Fall-events among people with stroke living in the community: Circumstances of falls and characteristics of fallers (Proceedings of SRR)
No full textObjectives: To describe the frequency and circumstances of falls among a community sample of people with stroke and to compare characteristics of fallers and nonfallers.Design: Cross-sectional, observational study.Setting: Community.Participants: Forty-one community-dwelling people with stroke (26 men, 15 women mean age, 69.7 ± 11.6y), of which 23 had right-hemisphere infarction, 16 left-hemisphere infarction, and 2 had a brainstem lesion. Time since onset of stroke ranged from 3 to 288 months (mean, 50mo).Interventions: Not applicable.Main Outcome Measures: Standardized tests were used to measure mobility, upper limb function, activities of daily living (ADL ability), and mood. Information about fall events was collected by using a questionnaire.Results: Twenty-one participants (50%) were classed as fallers, of whom 10 had fallen repeatedly. No significant differences were found between fallers and nonfallers on any of the measures used. However, those who had 2 or more falls (n = 10) had significantly reduced arm function (P = .018) and ADL ability (P = .010), compared with those who had not fallen or experienced near falls (n = 5). Loss of balance, misjudgment, and foot dragging during walking, turning, and sit to stand were reported by fallers as the suspected causes and activities leading to falls.Conclusions: The high risk of falling among people with stroke was evident in this community-based sample. Repeat fallers had greater mobility deficits and significantly reduced arm function and ADL ability than those who did not report any instability
A Structured Hardware/Software Architecture for Embedded Sensor Nodes
Get PDFOwing to the limited requirement for sensor processing in early networked sensor nodes, embedded software was generally built around the communication stack. Modern sensor nodes have evolved to contain significant on-board functionality in addition to communications, including sensor processing, energy management, actuation and locationing. The embedded software for this functionality, however, is often implemented in the application layer of the communications stack, resulting in an unstructured, top-heavy and complex stack. In this paper, we propose an embedded system architecture to formally specify multiple interfaces on a sensor node. This architecture differs from existing solutions by providing a sensor node with multiple stacks (each stack implements a separate node function), all linked by a shared application layer. This establishes a structured platform for the formal design, specification and implementation of modern sensor and wireless sensor nodes. We describe a practical prototype of an intelligent sensing, energy-aware, sensor node that has been developed using this architecture, implementing stacks for communications, sensing and energy management. The structure and operation of the intelligent sensing and energy management stacks are described in detail. The proposed architecture promotes structured and modular design, allowing for efficient code reuse and being suitable for future generations of sensor nodes featuring interchangeable components
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