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Search Results: 1 - 10 of 351 matches for " Siamak;Sewell "
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How should we assess the mechanical properties of lower-limb prosthesis technology used in elite sport?—An initial investigation  [PDF]
Bryce Dyer, Philip Sewell, Siamak Noroozi
Journal of Biomedical Science and Engineering (JBiSE) , 2013, DOI: 10.4236/jbise.2013.62015
Abstract:

Despite recent controversy, it is not yet formally recognised how lower-limb prosthesis should be assessed for their performance. To assist in this process, experiments are undertaken to investigate the linearity, stiffness and assessment of feet based energy return prosthesis technology typically used for elite level high speed running. Through initial investigations, it is concluded that static load testing would not be recommended to specify or regulate energy return prostheses for athletes with a lower-limb amputation. Furthermore, an assessment of energy return technology when loaded under dynamic conditions demonstrates changes in mechanical stiffness due to bending and effective blade length variation during motion. Such radical changes of boundary conditions due to loading suggest that any assessment of lower-limb prosthesis technology in the future should use methods that do not assume linear mechanical stiffness. The research into such effects warrants further investigation in the future.


Optimum Design of Fibre Orientation in Composite Laminate Plates for Out-Plane Stresses
Rasoul Khandan,Siamak Noroozi,Philip Sewell,John Vinney,Mehran Koohgilani
Advances in Materials Science and Engineering , 2012, DOI: 10.1155/2012/232847
Abstract: Previous studies have shown that composite fibre orientations can be optimised for specific load cases such as longitudinal or in-plane loading. However, the methodologies utilised in these studies cannot be used for general analysis of such problems. In this research, an extra term is added to the optimisation penalty function in order to consider the transverse shear effect. This modified penalty function leads to a new methodology whereby the thickness of laminated composite plate is minimized by optimising the fibre orientations for different load cases. Therefore, the effect of transverse shear forces is considered in this study. Simulated annealing (SA) is used to search for the optimal design. This optimisation algorithm has been shown to be reliable as it is not based on the starting point, and it can escape from the local optimum points. In this research, the Tsai-Wu failure and maximum stress criteria for composite laminate are chosen. By applying two failure criteria at the same time the results are more reliable. Experimentally generated results show a very good agreement with the numerical results, validating the simulated model used. Finally, to validate the methodology the numerical results are compared to the results of previous research with specific loading. 1. Introduction The demand for high strength, high modulus and low density industrial materials has generated an increased number of applications for fibre laminated composite structures in many different fields such as in submarines, sport equipment, medical instruments, civil engineering, enabling technologies, primary and secondary marine and aerospace structures, astronavigation and many more industries [1]. Composite constructions are usually multilayer produced structures, mostly made of flat and curved panels, built up from several layers or laminae, which are bonded together [2]. In the last half century, the use of composite materials has grown rapidly. These materials are ideal for structural applications that require high strength and low weight. They have good fatigue characteristics and are resistant to corrosion. They provide some flexibility in design through the variation of the fibre orientation or stacking sequence of fibre and matrix materials [3, 4]. Another advantage of fibre laminate composites is the capability to design the physical structure and mechanical properties prior to manufacture. The mechanical behaviour of laminates strongly depends on the orientation of fibres and thickness of lamina. Accordingly, the lamina should be designed to satisfy the
A semi-analytical model for deflection analysis of laminated plates with the Newton-Kantorovich-Quadrature method
Khandan, Rasoul;Noroozi, Siamak;Sewell, Philip;Vinney, John;Koohgilani, Mehran;
Materials Research , 2013, DOI: 10.1590/S1516-14392012005000174
Abstract: a semi-analytical approach for analysis of laminated plates with general boundary conditions under a general distribution of loads is developed. the non-linear equations are solved by the newton-kantorovich-quadrature (nkq) method which is a combination of well-known newton-kantorovich method and the quadrature method. this method attempts to solve a sequence of linear integral equations. the convergence of the proposed method is compared with other semi-analytical methods. the validation of the method is explored through various numerical examples and the results compared with finite element method (fem) and experimental tests. good agreement between the nkq model, fem and experimental results are shown to validate the model.
Gender (sic) Equality (sic)
Martin Sewell
Opticon1826 , 2008, DOI: 10.5334/opt.040813
Abstract: This article is a response to both a Letter to the Editor by Dr Ambily Banerjee (Banerjee, 2007) and the recent UCL Gender Equality Event. Dr Banerjee claimed to be ‘astounded’ to find a ‘glass ceiling’ (sic) within her own discipline, Anatomy. She concludes her letter with, ‘I have never believed motherhood is a valid excuse for not realising one’s potential’. Both points are wrongheaded, and are the result of bogus feminist thinking. Firstly, men and women are different; and secondly, we have evolved ‘as if’ reproduction is the sole goal for which human beings were ‘designed’ and everything else is a means to that end. Feminism not only harms men, but harms women like Dr Banerjee, too (Quest, 1994; Sommers, 1995). Indeed, women are less happy today than they were in the 1970s and ‘the changes brought about through the women’s movement may have decreased women’s happiness’ (Stevenson and Wolfers, 2007).
Physical and chemical stability of cisplatin infusions in PVC containers
Graham Sewell
European Journal of Oncology Pharmacy , 2010,
Abstract: Study objectives: To determine the extended chemical and physical stability of cisplatin infusions in PVC containers at normal in-use concentrations in saline, with and without added electrolyte combinations relevant to clinical practice. Methods: Cisplatin infusions 0.1–0.4 mg/mL were prepared in normal saline, with and without magnesium sulphate and potassium chloride supplements in 500 mL PVC bags, and stored at 25°C protected from light. Chemical stability was assessed by a stability-indicating LC method. Evidence for precipitation was detected by a light-blocking particle count method for sub-visible particles, supported by visual examination. pH and weight changes were also monitored for at least 28 days. Results: Both 0.1 mg/mL and 0.4 mg/mL infusions, with or without the added electrolyte supplements, were chemically stable over 28 days at 25°C. The pH of infusions varied by no more than 0.2 units over this time, there was no visible precipitation, and no significant changes in sub-visual particulate levels or infusion weight. The study was restricted to 28 days because small, visual precipitation was evident in some infusions after 35 days. Conclusion: Cisplatin infusions at concentrations ranging from 0.1–0.4 mg/mL, in 500 mL PVC bags containing either 0.9% sodium chloride or 0.9% sodium chloride + 20 mmoL KCl + 8 mmoL MgSO4 were physically and chemically stable for up to 28 days at 25°C, when protected from light. Extending shelf lives beyond this period is unsafe due to the potential development of precipitates.
Can the Quantum Measurement Problem be resolved within the framework of Schroedinger Dynamics and Quantum Probability?
Geoffrey Sewell
Physics , 2007, DOI: 10.1063/1.2827306
Abstract: We provide an affirmative answer to the question posed in the title. Our argument is based on a treatment of the Schroedinger dynamics of the composite of a quantum microsystem, S, and a macroscopic measuring apparatus, I, consisting of N interacting particles. The pointer positions of this apparatus are represented by orthogonal subspaces of its representative Hilbert space that are simultaneous eigenspaces of coarse-grained macroscopic observables. By taking explicit account of their macroscopicality via a large deviation principle, we prove that, for a suitably designed apparatus I, the evolution of the composite (S+I) leads both to the reduction of the wave packet of S and to a one-to-one correspondence between the resultant state of this microsystem and the pointer position of I, up to utterly negligible corrections that decrease exponentially with N.
On Connections between the Quantum and Hydrodynamical Pictures of Matter
Geoffrey Sewell
Physics , 2007,
Abstract: We present a general, model-independent, quantum statistical treatment of the connection between the quantum and hydrodynamical pictures of reservoir driven macroscopic systems. This treatment is centred on the large scale properties of locally conserved hydrodynamical observables and is designed to form a bridge between quantum microdynamics and classical macroscopic continuum mechanics, rather than a derivation of the latter from the former. The key assumptions on which the treatment is based are hypotheses of chaoticity and local equilibrium for the hydrodynamical fluctuations around nonequilibrium steady states, together with an extension of Onsager's regrssion hypothesis to those states. On this basis, we establish canonical generalisations of both the Onsager reciprocity relations and the Onsager-Machlup fluctuation theory to nonequilibrium steady states, and we show that the spatial correlations of the hydrodynamical fluctuations are generically of long range in these states.
Quantum stochastic models with hydrodynamical behaviour
Geoffrey Sewell
Physics , 2006, DOI: 10.1016/S0034-4877(07)80037-1
Abstract: We construct a class of quantum stochastic models of reservoir driven many-particle systems that are the natural counterparts of certain extensively studied classical ones, which have been shown to exhibit good hydrodynamical behaviour. Our treatment of these models achieves two main aims. The first is to show that they enjoy the hydrodynamical properties of their classical counterparts. The second is to show that they satisfy the key assumptions of the general quantum macrostatistical scheme, presented in earlier works by the author, which served to expose certain generic large scale features of nonequilibrium steady states, e.g. the long range of the hydrodynamical correlations that they carry. In this way we establish the viability of that scheme.
On Order, Disorder and Coherence
Geoffrey Sewell
Physics , 2007,
Abstract: We provide a brief survey of quantum statistical characterisations of order, disorder and coherence in systems of many degrees of freedom. Here, order and coherence are described in terms of symmetry breakdown, while disorder is described in terms of entropy and algorithmic complexity, whose interconnection has been recently extended from the classical to the quantum domain. We see that, in the present physical context, the concepts of order and disorder are not mutually antithetical, but bear an interrelationship similar to that between signals and noise.
On the mathematical Structure of Quantum Measurement Theory
Geoffrey Sewell
Mathematics , 2005, DOI: 10.1016/S0034-4877(05)80074-6
Abstract: We show that the key problems of quantum measurement theory, namely the reduction of the wave packet of a microsystem and the specification of its quantum state by a macroscopic measuring instrument, may be rigorously resolved within the traditional framework of the quantum mechanics of finite conservative systems. The argument is centred on the generic model of a microsystem, S, coupled to a finite macroscopic measuring instrument, I, which itself is an N-particle quantum system. The pointer positions of I correspond to the macrostates of this instrument, as represented by orthogonal subspaces of the Hilbert space of its pure states. These subspaces, or 'phase cells', are the simultaneous eigenspaces of a set of coarse grained intercommuting macroscopic observables, M, and, crucially, are of astronomically large dimensionalities, which incease exponentially with N. We formulate conditions on the conservative dynamics of the composite (S+I) under which it yields both a reduction of the wave packet describing the state of S and a one-to-one correspondence, following a measurement, between the pointer position of I and the resultant state of S; and we show that these conditions are fulfilled by the finite version of the Coleman-Hepp model.
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