ECG Round: A man with dizziness

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A six-node pentagonal assumed natural strain solid-shell element

In this paper, a six-node pentagonal solid-shell element is formulated. Particular attention is focused on alleviating shear, trapezoidal and thickness lockings that plagues the conventional element. While assumed natural strain method is employed to alleviate shear and trapezoidal lockings, a modified generalized laminate stiffness matrix is proposed to circumvent thickness locking. Unlike the commonly adopted plane stress assumption, the modified laminate stiffness matrix enables the element to reproduce the exact thickness stress and transverse displacement when the element is loaded by thickness stress. Numerical examples reveal that the element is close in accuracy with other state-of-the-art three-node degenerated shell elements. © 2001 Elsevier Science B.V.postprin

ECG Round: A lady with dyspnoea

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ECG Round: A lady with palpitation

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ECG Round: Cardiac arrest

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The effect of flow coefficient on the design of miniature centrifugal impeller

This paper was presented at the 3rd Micro and Nano Flows Conference (MNF2011), which was held at the Makedonia Palace Hotel, Thessaloniki in Greece. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, Aristotle University of Thessaloniki, University of Thessaly, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute.A systematic and simple design methodology of miniature centrifugal impeller is proposed. In the design of miniature centrifugal impeller, the flow coefficient ϕ1 plays a significant role. Theoretically, the geometric parameters, including inner radius, blade angles and blade height can be expressed as functions of the flow coefficient. Accordingly, the theoretical head and energy losses are also influenced by the flow coefficient. To investigate the effect of flow coefficient, a series of miniature impellers are designed for different flow coefficients, and CFD simulations are conducted. Both theoretical analysis and CFD simulations show similar trends. Initially, the pressure generated increases with increasing flow coefficient. Upon reaching a maximum, it will subsequently decrease with increasing flow coefficient. Hence, an optimal flow coefficient should be chosen to achieve the best performance. From the theoretical results, the maximum pressure generated occurs when the flow coefficient is approximately 2.8, while for CFD, it is approximately 1.3. The difference between the theoretical analysis and CFD simulation shows that the theoretical model should be further improved to enhance its accuracy

Piezoelectric and pyroelectric properties of PT/P(VDF-TrFE) 0-3 composites

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B-spline snakes in two stages

In using Snake algorithms, the slow convergence speed is due to the large number of control points to be selected, as well as difficulties in setting the weighting factors that comprise the internal energies of the curve. Even in using the B-Spline snakes, splines cannot be fitted into the corner of the object completely. In this paper, a novel two-stage method based on B-Spline Snakes is proposed. It is superior both in accuracy and fast convergence speed over previous B-Spline Snakes. The first stage reduces the number of control points using potential function V(x,y) minimization. Hence, it allows the spline to quickly approach the minimum energy state. The second stage is designed to refine the B-Spline snakes based on the node points of the polynomials without knots. In other words, an elasticity spline is controlled by node points where knots are fixed. Simulation and validation of results are presented. Compared to the traditional B-Spline snakes, better performance was achieved using the method proposed in this paper.published_or_final_versio

Descriptive Anatomy and Three-Dimensional Reconstruction of the Skull of the Early Tetrapod Acanthostega gunnari Jarvik, 1952

The early tetrapod Acanthostega gunnari is an iconic fossil taxon exhibiting skeletal morphology reflecting the transition of vertebrates from water onto land. Computed tomography data of two Acanthostega skulls was segmented using visualization software to digitally separate bone from matrix and individual bones of the skull from each other. A revised description of cranial and lower jaw anatomy in this taxon based on CT data includes new details of sutural morphology, the previously undescribed quadrate and articular bones, and the mandibular symphysis. Sutural morphology is used to infer loading regime in the skull during feeding, and suggests Acanthostega used its anterior jaws to initially seize prey while smaller posterior teeth were used to restrain struggling prey during ingestion. Novel methods were used to repair and retrodeform the skull, resulting in a three-dimensional digital reconstruction that features a longer postorbital region and more strongly hooked anterior lower jaw than previous attempts while supporting the presence of a midline gap between the nasals and median rostrals

Pyroelectric and piezoelectric properties of lead titanate/polyvinylidene fluoride-trifluoroethylene 0-3 composites

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