180,971 research outputs found
Conservative Deterministic Spectral Boltzmann Solver Near The Grazing Collisions Limit
No full textWe present new results building on the conservative deterministic spectral method for the space homogeneous Boltzmann equation developed by Gamba and Tharkabhushaman. This approach is a two-step process that acts on the weak form of the Boltzmann equation, and uses the machinery of the Fourier transform to reformulate the collisional integral into a weighted convolution in Fourier space. A constrained optimization problem is solved to preserve the mass, momentum, and energy of the resulting distribution. Within this framework we have extended the formulation to the case of more general case of collision operators with anisotropic scattering mechanisms, which requires a new formulation of the convolution weights. We also derive the grazing collisions limit for the method, and show that it is consistent with the Fokker-Planck-Landau equations as the grazing collisions parameter goes to zero.Mathematic
Lezioni di Anatomia descrittiva-esterna applicata alle Arti Belle ad uso degli Allievi della R. Accademia Albertina per il Dottore Cav. Alberto Gamba
No full textIl volume contiene 50 tavole litografiche che rappresentano in modo particolareggiato le varie parti del corpo umano. Sono appunto delle lezioni che sono state riprodotte come supporto allo studio dell\u27Anatomia per gli allievi della R. Accademia Albertina. L\u27autore è il Dott. Cav. Alberto Gamba. L\u27opera è stata stampata a Torino nel 1862. L\u27Accademia Albertina delle Belle Arti di Torino è una delle più antiche d\u27Italia, è stata fondata nel 1652 e occupa l\u27attuale sede dal 1832 per volontà di Re Carlo Alberto
A Fast Conservative Spectral Solver For The Nonlinear Boltzmann Collision Operator
No full textWe present a conservative spectral method for the fully nonlinear Boltzmann collision operator based on the weighted convolution structure in Fourier space developed by Gamba and Tharkabhushnanam.. This method can simulate a broad class of collisions, including both elastic and inelastic collisions as well as angularly dependent cross sections in which grazing collisions play a major role. The extension presented in this paper consists of factorizing the convolution weight on quadrature points by exploiting the symmetric nature of the particle interaction law, which reduces the computational cost and memory requirements of the method to O(M(2)N(4)logN) from the O(N-6) complexity of the original spectral method, where N is the number of velocity grid points in each velocity dimension and M is the number of quadrature points in the factorization, which can be taken to be much smaller than N. We present preliminary numerical results.Mathematic
High performance computing with a conservative spectral Boltzmann solver
No full textAbstract. We present new results building on the conservative deterministic spectral method for the space inhomogeneous Boltzmann equation developed by Gamba and Tharkabhushaman. This approach is a two-step process that acts on the weak form of the Boltzmann equation, and uses the machinery of the Fourier transform to reformulate the collisional integral into a weighted convolution in Fourier space. A constrained optimization problem is solved to preserve the mass, momentum, and energy of the resulting distribution. We extend this method to second order accuracy in space and time, and explore how to leverage the structure of the collisional formulation for high performance computing environments. The locality in space of the collisional term provides a straightforward memory decomposition, and we perform some initial scaling tests on high performance computing resources. We also use the improved computational power of this method to investigate a boundary-layer generated shock problem that cannot be described by classical hydrodynamics
R&D and market size: who benefits from orphan drug regulation?
No full textSince the early 80s, orphan drug regulations have been introduced to stimulate R&D for
rare diseases. We develop a theoretical model to study the heterogeneous impact on optimal R&D decisions of the incentives for diseases with different levels of prevalence. We
show the mechanisms through which the type of incentives deployed by orphan drug regulations may stimulate R&D more for orphan diseases with comparatively high prevalence,
thus increasing inequality within the class of orphan diseases. Using data from the Food and
Drug Administration on the number of orphan designations, our empirical analysis shows
that, while R&D has increased over time for all orphan diseases, the increase has been much
greater for the less rare. According to our baseline specification, the difference between
the predicted number of orphan designations for a disease belonging to the highest and the
lowest class of prevalence is 5.6 times larger after 2008 than it was in 1983. Our findings
support the idea that the type of incentives in place may be responsible for this increase in
inequality within orphan diseases
A method based on random-fuzzy variables for on-line estimation of the measurement uncertainty of DPS-based instruments
No full textThe evaluation of the uncertainty of the result of a
measurement performed by a DSP-based instrument is usually a complex and difficult task. The sources of uncertainty are the instrument input stage and the analog-to-digital converter (ADC), so that each input sample to the instrument can be considered a measurement result with its associated uncertainty. The uncertainty on the final measurement result is obtained as the combination of the uncertainty values of each sample, according to the measurement algorithm implemented on the digital signal processing (DSP) system. This paper proposes an innovative approach, based on the representation of the measurement result and its associated uncertainty in terms of random-fuzzy variables, that, after having suitably characterized the metrological performance of the input
stage and analog-to-digital converter, provides an online estimation of the measurement uncertainty. The method has been validated experimentally, and the results of the experimental work are reported
CAMPAGNA NELLA CORTE. Progetto per la tipica casa campana. Firmata da Massimiliano Rendina ripristina il cortile rurale.
No full textUna descrizione approfondita della casa rurale di Ruviano, con riferimenti alla casa pompeiana e quella a corte delle campagne campane
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