BIRD, BCAM's Institutional Repository Data
http://bird.bcamath.org:80
The BIRD digital repository system captures, stores, indexes, preserves, and distributes digital research material.2017-07-22T01:58:00ZMonotonicity and convexity of the ratios of the first kind modified Bessel functions and applications
http://hdl.handle.net/20.500.11824/698
Monotonicity and convexity of the ratios of the first kind modified Bessel functions and applications
Yang Z-H.; Zheng S.
Let $I_{v}\left( x\right) $ be modified Bessel functions of the first
kind. We prove the monotonicity property of the function $x\mapsto
I_{u}\left( x\right) I_{v}\left( x\right) /I_{\left( u+v\right) /2}\left(
x\right) ^{2}$ on $\left( 0,\infty \right) $. As a direct consequence, it deduces some known results including Tur\'{a}n-type inequalities and log-convexity or log-concavity of $I_{v}$ in $v$, as well as it yields some new and interesting monotonicity and convexity concerning the ratios of modified Bessel functions of the first kind. In addition, a few of sharp bounds involving $I_{v}\left( x\right) $ and their ratios are presented.
2017-07-18T00:00:00ZHartree-Fock theory with a self-generated magnetic field
http://hdl.handle.net/20.500.11824/697
Hartree-Fock theory with a self-generated magnetic field
Comelli S.; Garcia-Cervera C.J.
We prove the existence of a ground state within the Hartree-Fock theory for atoms and molecules, in the presence of self-generated magnetic fields, with and without direct spin coupling. The ground state exists provided that the total charge Z of the K nuclei exceeds N, where N is the number of electrons, and, in the spin-polarized case, provided in addition that the nuclear charge is not too high.
2017-06-01T00:00:00ZA simple Bayesian linear excess relative risk model
http://hdl.handle.net/20.500.11824/696
A simple Bayesian linear excess relative risk model
Higueras M.; Harbron R.W.; Pearce M.S.
A new Bayesian Poisson relative risk model is proposed for displaying the excess relative risk associated to a unique exposure as a probability distribution in a closed form. The background risk can be modelled by a unique two levels factor, e.g. gender or smoking status.
2017-07-11T00:00:00ZTowards HPC-Embedded Case Study: Kalray and Message-Passing on NoC
http://hdl.handle.net/20.500.11824/695
Towards HPC-Embedded Case Study: Kalray and Message-Passing on NoC
Valero-Lara P.; Krishnasamy E.; Jansson J.
Today one of the most important challenges in HPC is the development of computers with a low power consumption. In this context, recently, new embedded many-core systems have emerged. One of them is Kalray. Unlike other many-core architectures, Kalray is not a co-processor (self-hosted). One interesting feature of the Kalray architecture is the Network on Chip (NoC) connection. Habitually, the communication in many-core architectures is carried out via shared memory. However, in Kalray, the communication among processing elements can also be via Message-Passing on the NoC. One of the main motivations of this work is to present the main constraints to deal with the Kalray architecture. In particular, we focused on memory management and communication. We assess the use of NoC and shared memory on Kalray. Unlike shared memory, the implementation of Message-Passing on NoC is not transparent from programmer point of view. The synchronization among processing elements and NoC is other of the challenges to deal with in the Karlay processor. Although the synchronization using Message-Passing is more complex and consuming time than using shared memory, we obtain an overall speedup close to 6 when using Message-Passing on NoC with respect to the use of shared memory. Additionally, we have measured the power consumption of both approaches. Despite of being faster, the use of NoC presents a higher power consumption with respect to the approach that exploits shared memory. This additional consumption in Watts is about a 50%. However, the reduction in time by using NoC has an important impact on the overall power consumption as well.
2017-01-01T00:00:00Z