395 research outputs found
How the scars of past wars continue to shape UK society
No full textEdward Pinchbeck, Felipe Carozzi and Luca Repetto discuss new research exploring how memory of losses from war affects communities and shapes social values. Their findings suggest the impact can reverberate through generations
Nonlinear BEM-surface impedance boundary condition formulation for unstructured meshes
No full textSurface impedance boundary conditions are used to
take into account electromagnetic phenomena in thin layers. By
exploiting a dual geometrical discretisation of the surface of a
conducting object, it can be used to formulate the skin effect as a
circuit. The mesh can be either structured or unstructured as in
case of triangular elements. The surface circuit can be coupled to
a boundary element method for the region surrounding it giving
rise to a hybrid solution. Field distribution along the depth of
the conductor can account for nonlinearity if the analytical one
dimensional solution is replaced by a numerical one. The hybrid
technique is applied to the analysis of induction heating devices
Algebraic formulation of nonlinear surface impedance boundary condition coupled with BEM for unstructured meshes
No full textThis paper deals with nonlinear eddy currents problems introducing a novel surface impedance boundary conditions (SIBC). The SIBC is formulated in the algebraic framework giving to the field problem a circuital interpretation. In this way, the material behavior of the conductive computational domain is described by a network of lumped components. This paper shows that this matrix can be defined analytically in the case of linear magnetic characteristic or numerically when the material is nonlinear. It is shown that by mapping the magnetic nonlinearity into the circuit matrix the nonlinearity of the problem is smoothed and, therefore, a simple iterative scheme can be used. The SIBC is coupled to a BEM (for the region surrounding) giving rise to a hybrid solution. The method has been tested in terms of efficiency and accuracy. The use of the Schur complement of the solution matrix has allowed to decrease the solution time of an order of magnitude. A block triangular preconditioner is finally proposed in the case of highly distorted elements of the mesh. The preconditioner is based on the sparsification of the BEM matrix and its performance are analyzed considering a benchmark problem and a real problem (a wireless power transfer system). (C) 2017 Elsevier Ltd. All rights reserved
Lensless digital holographic microscope with light-emitting diode illumination
No full textWe demonstrate the operation of a digital in-line microscope with LED illumination. We show with a practical example that, for typical setups, the limited temporal coherence and the spatial incoherence of the source do not affect the resolving power of the system. On the contrary, important advantages are obtained in terms of signal-to-noise ratio and alignment simplification
Energy harvesting from bearings rotation in a seeding agriculture machine
No full textEnergy harvesting is one of the emerging sustainable and innovative solutions for supplying energy to remote sensors for the IoT world. This process is going on also in the agricultural sector where the need to monitor machines devoted to farming and other agricultural activities is growing. In particular, it addresses the energy needs of agriculture while minimizing its ecological impact. In this work, the energy harvesting technology is exploited to remotely monitor the performances of seeding disk bearings. Specifically, an harvester that collects the rotating kinetic energy of seeding disks is designed to detect if they are properly working. When the seeding disks are rotating, electric power is generated and a signal is sent ensuring everything is in order. However, in the event of a malfunction, no electrical power is produced, leading to the activation of a warning on the main board which notifies about the malfunctioning of a seeding disk. The design of the harvester is based on an axial flux generator topology and it is developed by performing evaluations on the reaction torque to counteract the magnetic attractive force and on the electromotive force which can be harvested in order to send the signal. By developing and implementing this energy harvesting technology for remote monitoring, this work aims to improve the efficiency and reliability of agricultural machines, ultimately contributing to increased productivity and reduced downtime in farming operations
Multicriteria design of an electromagnetic hammer
No full textIn this paper, a Pareto based multicriteria design procedure for a linear motor driving an electromagnetic demolition hammer is presented. The hammer application requires high dynamical performance as it must deliver at the same time high value of impact energy and frequency of cycle. The uncertain characteristic of the medium on which the hammer head will impact has to be taken into account in an integrated electromechanical model of the system that could guide the control strategy of the supply system. Requirements of the application are stated and some preliminary analysis that lead to the choice of a Linear Permanent Magnet Synchronous Motor are described. The integrated electromechanical model, taking into account the modelling of the head impact on the soil is described. Some of the principal results show that the solution is not unique but comes out of a spread of possibilities so that Pareto criterion is used to sort them out. Simulation results obtained on the main operative hammer quantities are presented and discussed
Identification of equivalent material properties for 3D numerical modelling of induction heating in ferromagnetic workpieces
No full textREFERENCE LEAKAGE DEVICE FOR LEAK CALIBRATION
No full textReference leakage device (1) for use in leakage detection of gas, comprises a membrane (5) adapted to be interposed between two environments having respective pressures pu and pa, where (I). The membrane has an orifice (6) adapted to determine a controlled gas flow depending on the pressure pu. The orifice has a preset diameter D and length L such that (II). The diameter D and the length L are further dimensioned in such a manner that the equivalent diameter De of the orifice is De≦100 nm, where De is defined by the relation De=D.a1/2 wherein a is the transmission probability of the orifice, function of the L/D ratio. The orifice is adapted to operate in molecular flow regime in an entire range of pυ values comprising the value of atmospheric pressure
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