Computer aided design of nonlinear control systems via optimization

Imperial Users onl

Spare parts provisioning for multiple k-out-of-n:G systems

In this paper, we consider a repair shop that fixes failed components from different k-out-of-n:G systems. We assume that each system consists of the same type of component; to increase availability, a certain number of components are stocked as spare parts. We permit a shared inventory serving all systems and/or reserved inventories for each system; we call this a hybrid model. Additionally, we consider two alternative dispatching rules for the repaired component. The destination for a repaired component can be chosen either on a first-come-first-served basis or by following a static priority rule. Our analysis gives the steady-state system size distribution of the two alternative models at the repair shop. We conduct numerical examples minimizing the spare parts held while subjecting the availability of each system to exceed a targeted value. Our findings show that unless the availabilities of systems are close, the HP policy is better than the HF policy

Cognitive, social and emotional processes in unawareness of illness following stroke

Includes bibliographical referencesDisturbances in unawareness can offer an important avenue to investigate the neurocognitive processes involved in the construction of the bodily self. The general aim of the present thesis was to advance the current state of knowledge on a prototypical disorder of self-awareness, anosognosia for hemiplegia (AHP): unawareness of motor deficits contralateral to a brain lesion. Based on insights gained from both clinical and experimental research on anosognosia, it is argued that purely sensorimotor accounts do not explain several features of the syndrome, such as the delusional and emotional aspects. Therefore a revision of prevailing, modular theories of anosognosia is proposed that take into account the involvement of affective and so cial processes. Accordingly, the thesis aimed to: (1) investig ate the emotional and social factors that underlie motor unawareness; (2) identify the neurocognitive factors and neuroanatomical correlate that underlie such factors; and (3) develop potential, bedside rehabilitation interventions for AHP that are informed by the above investigations. These aims were achieved using an integrative methodological approach, which combined neuropsychological testing, psychophysiological experiments and neuroimaging methods. A series of experiment al group investigations and clinical case studies were conducted in 53 adult patients with right-hemisphere strokes. The main results of these studies showed that: (i) motor awareness is modulated by negative, but not positive emotion in a social context; (ii) anosognosia is associated with specific deficits in 3rd person perspective taking in visual-spatial and mentalising tasks; (iii) anosognosia is modulated by 'other' referent and 3rd person verbal and visual perspective taking. These experimental findings on the role of emotion and social processes in AHP were in turn used to develop a rehabilitation intervention applied in two case studies that showed promising results. Additionally, converging neuroimaging evidence provided support for the unique involvement of the inferior frontal gyrus, insula ribbon, supramarginal and superior temporal gyrus, and dorsal frontal white matter in anosognosia, which have well-established links to motor monitoring, subjecting feelings and self-awareness, and the proposed 'mentalising network'. These finding are in support of a proposed new account of AHP, which move s away from traditional modular theories of anosognosia, towards a dynamic model of the construction of the bodily self

Is Vitamin D Supplementation Effective in Improving Physical Performance in Older Patients With Heart Failure Who Are Over the Age of 50 Years?

OBJECTIVE: The objective of this selective EBM review is to determine whether or not vitamin D supplement is effective in improving physical performance in older patients with heart failure over the age 50 years STUDY DESIGN: Review of three English language primary studies, two published in 2010 and one was published in 2013. DATA SOURCES: Two double blind randomized controlled trials (RCT) and one cross-sectional study that investigated the use of vitamin D in improving physical performance in heart failure. Sources were selected and found using PubMed, ScienceDirect, and Cochrane databases. OUTCOMES MEASURED: The outcomes measured were improvement of physical performance, and associations among muscle strength, health status measures, and serum vitamin D. Tools used to measure were, a 6 minute walk distance test (6MWD), timed get up and go test (TGUG), isokinetic muscle testing. RESULTS: The results of two RCT studies Boxer et al. (2013) and Witham et al. (2013) supported that vitamin D does not improve physical performance. The Boxer et al. (2010) cross-sectional study showed no association among serum vitamin D concentration, muscle strength, and health status. Boxer et al. (2013) and Witham et al. (2013) demonstrated that the 6MWD test and TGUG test did not improve with physical activity. CONCLUSION: The results of the RCT’s and the cross-sectional study reviewed; suggest that Vitamin D does not improve the physical performance of older adults with heart failure. This topic does warrant additional research. Further studies conducted should include more frequent, lower doses of vitamin D and examine the results for a longer period of time. The effects of sun-exposure on vitamin D concentration and improvement of physical activity also should be investigated