6,998 research outputs found
Haemorrhaging lesion in the breast: is there a role for embolisation?
Angiosarcoma of the breast is an extremely rare condition. This case illustrates the use of embolisation as a modality of treatment for primary breast angiosarcoma. No other case has been reported on the use of embolisation for this disorder
Assessing Gender Identity and Sex in Diverse Low, Middle, and High-Income Settings: Findings from a WHO/HRP Consultative Process
Obtaining detailed data on gender identity and sex in population-based sexual health studies is important. We convened a group to develop consensus survey items. We identified two items to capture data on gender identity and sex that can be used in diverse settings
Manipulation of the spin helix in FeGe thin films and FeGe/Fe multilayers
Magnetic materials without structural inversion symmetry can display the Dzyaloshinskii-Moriya interaction, which manifests itself as chiral magnetic ground states. These chiral states can interact in complex ways with applied fields and boundary conditions provided by finite sample sizes that are of the order of the lengthscale of the chiral states. Here we study epitaxial thin films of FeGe with a thickness close to the helix pitch of the helimagnetic ground state, which is about 70 nm, by conventional magnetometry and polarized neutron reflectometry. We show that the helix in an FeGe film reverses under the application of a field by deforming into a helicoidal form, with twists in the helicoid being forced out of the film surfaces on the way to saturation. An additional boundary condition was imposed by exchange coupling a ferromagnetic Fe layer to one of the interfaces of an FeGe layer. This forces the FeGe spins at the interface to point in the same direction as the Fe, preventing node expulsion and giving a handle by which the reversal of the helical magnet may be controlled
Development of a generic activities model of command and control
This paper reports on five different models of command and control. Four different models are reviewed: a process model, a contextual control model, a decision ladder model and a functional model. Further to this, command and control activities are analysed in three distinct domains: armed forces, emergency services and civilian services. From this analysis, taxonomies of command and control activities are developed that give rise to an activities model of command and control. This model will be used to guide further research into technological support of command and control activities
Approach for the determination of heat transfer coefficients for filling process of pressure vessels with compressed gaseous media
Paper presented at the 6th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 30 June - 2 July, 2008.For fast and effective simulation of filling processes of
pressure vessels with compressed gaseous media the governing
equations are derived from a mass balance equation for the gas
and from energy balance equations for the gas and the wall of
the vessel. For simplicity the gas is considered as a perfectly
mixed phase and two heat transfer coefficients are introduced.
The first one is the mean heat transfer coefficient between the
gas and the inner surface of the pressure vessel and the second
one is the heat transfer coefficient between outer surface of the
vessel and the surroundings. Although the process is transient,
steady-state heat transfer coefficients for free convection are
used between outer surface of the vessel and the surroundings.
The use of available correlations for steady-state heat transfer
coefficients to describe transient processes is common practice,
e.g. in the modelling of the transient behaviour of heat
exchangers [1]. But no correlations – neither steady-state nor
transient – are available for the heat transfer coefficient
between inflowing gas and inner surface of the vessel. To solve
this problem a CFD tool is used to determine the gas velocities
at the vicinity of the inner surface of the vessel for a number of
discrete surface elements. The results of a large amount of
numerical experiments show that there exists a unique
relationship between the tangential fluid velocities at the
vicinity of the inner surface of the vessel and the gas velocity at
the inlet. Once this unique relationship is known the complete
velocity distribution at the vicinity of the inner surface can be
easily calculated from the inlet velocity of the gas. The nearwall
velocities at the outer limit of the boundary layer are
substituted into the heat transfer correlation for external flow
over flat plates. The final heat transfer coefficient is the areaweighted
mean of all local heat transfer coefficients. The
method is applied to the special case of filling a 70 MPa
composite vessel for fuel cell vehicles with hydrogen. Because
of the heat capacity of the composite wall consisting of an inner
aluminium liner wrapped with carbon fibre, heat transfer from
the compressed gas to the vessel wall strongly influences the
temperature field of the gas which is predicted by the model
and confirmed by experiments.vk201
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