220 research outputs found
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A second-order slip model for arbitrary accomodation at the wall
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.We present a kinetic-theory derivation of second-order slip boundary conditions for a
plane isothermal pressure driven gas owing through a microchannel. In the proposed approach, the distribution function is expanded in terms of orthogonal polynomials and the system of moment equations in the expansion coefficients is analytically solved. The velocity slip coefficients, as well as their Knudsen layer corrections, are obtained by evaluating the solution in the near continuum limit. In comparison with other methods, the present approach is accurate and easy to implement. The results are presented for the Bhatnagar-Gross-Krook-Welander (BGKW) kinetic model equation and Maxwell's boundary conditions, but can be extended to more general collision integral and different scattering kernels.Fondazione Cariplo within the framework of the project Surface interactions in micro/nano device
Non-continuum effects on the sound of a heated line source: from a monopole to non-isotropic radiation
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Solving the Boltzmann equation on GPU’s
This paper was presented at the 2nd Micro and Nano Flows Conference (MNF2009), which was held at Brunel University, West London, UK. The conference was organised by Brunel University and supported by the Institution of Mechanical Engineers, IPEM, the Italian Union of Thermofluid dynamics, the Process Intensification Network, HEXAG - the Heat Exchange Action Group and the Institute of Mathematics and its Applications.We present algorithms specifically tailored for solving kinetic equations onto graphics processing units. Unlike particle methods, the proposed methods of solution are ideally suited for solving the unsteady low speed flows which typically occur inMEMS containing oscillating components. The efficiency of the algorithms is demonstrated by solving the two-dimensional low Mach number driven cavity flow of a monatomic gas. Computational results show that it is possible to cut down the computing time of the sequential codes up to two order of magnitudes. The algorithms can easily be extended to three-dimensional flows and to non-equilibrium flows of mixtures
A kinetic theory description of liquid menisci at the microscale
A kinetic model for the study of capillary flows in devices with microscale geometry is presented. The model is based on the Enskog-Vlasov kinetic equation and provides a reasonable description of both fluid-fluid and fluid-wall interactions. Numerical solutions are obtained by an extension of the classical Direct Simulation Monte Carlo (DSMC) to dense fluids. The equilibrium properties of liquid menisci between two hydrophilic walls are investigated and the validity of the Laplace-Kelvin equation at the microscale is assessed. The dynamical process which leads to the meniscus breakage is clarified
Bleaching melanin in formalin-fixed and paraffin-embedded melanoma specimens using visible light : a pilot study
In fluorescence microscopy, light radiation can be used to bleach fluorescent
molecules in formalin-fixed and paraffin-embedded (FFPE) samples, in order to
increase the ratio between signal of interest and background autofluorescence. We
tested if the same principle can be exploited in bright field microscopy to
bleach pigmented melanoma FFPE sections together with cell morphology
maintenance. After dewaxing and rehydration, serial FFPE sections of a feline
diffuse iris melanoma, a canine dermal melanoma, a gray horse dermal melanoma and
a swine cutaneous melanoma were irradiated with visible light for 1, 2, 3, 4 and
5 days, prior to Hematoxylin and Eosin staining. Complete bleaching was obtained
after 1-day treatment in feline and swine melanomas, while 2 and 3 days were
required in canine and equine neoplasms, respectively. In all treated samples,
cell morphology was maintained. Photo-induced bleaching combined with
immunohistochemistry was tested after a 3-day photo-treatment using five
different markers. According to the literature, in all samples neoplastic cells
stained positive for vimentin, S100 and PNL2, while negative for FVIII and
pancytokeratin. In conclusion, visible light can be effectively exploited to
bleach pigmented melanoma FFPE sections prior to perform routine histochemical
and immunohistochemical stains
Solving the Boltzmann Equation on GPU
We show how to accelerate the direct solution of the Boltzmann equation using
Graphics Processing Units (GPUs). In order to fully exploit the computational
power of the GPU, we choose a method of solution which combines a finite
difference discretization of the free-streaming term with a Monte Carlo
evaluation of the collision integral. The efficiency of the code is
demonstrated by solving the two-dimensional driven cavity flow. Computational
results show that it is possible to cut down the computing time of the
sequential code of two order of magnitudes. This makes the proposed method of
solution a viable alternative to particle simulations for studying unsteady low
Mach number flows.Comment: 18 pages, 3 pseudo-codes, 6 figures, 1 tabl
Coupling Molecular Dynamics and Direct Simulation Monte Carlo using a general and high-performance code coupling library
Volume, asymmetry and reciprocal relationships between paranasal sinuses: a 3D segmentation study on head CT-scans
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