3,862 research outputs found
Dynamics of a Rydberg hydrogen atom near a topologically insulating surface
We investigate the classical dynamics of a Rydberg hydrogen atom near the
surface of a planar topological insulator. The system is described by a
Hamiltonian consisting of the free-hydrogen part and the hydrogen-surface
potential. The latter includes the interactions between the electron and both
image electric charges and image magnetic monopoles. Owing to the axial
symmetry, the component of angular momentum is conserved. Here we
consider the case. The structure of the phase space is explored
extensively by means of numerical techniques and Poincar\'{e} surfaces of
section for the recently discovered topological insulator TlBiSe. The
phase space of the system is separated into regions of vibrational and
rotational motion. We show that vibrational-rotational-vibrational type
transitions can be tuned with the topological magnetoelectric polarizability.Comment: Accepted for publication in Europhysics Letter
A versatile trigger and synchronization module with IEEE1588 capabilities and EPICS support.
Event timing and synchronization are two key aspects to improve in the implementation of distributed data acquisition (dDAQ) systems such as the ones used in fusion experiments. It is also of great importance the integration of dDAQ in control and measurement networks. This paper analyzes the applicability of the IEEE1588 and EPICS standards to solve these problems, and presents a hardware module implementation based in both of them that allow adding these functionalities to any DAQ. The IEEE1588 standard facilitates the integration of event timing and synchronization mechanisms in distributed data acquisition systems based on IEEE 803.3 (Ethernet). An optimal implementation of such system requires the use of network interface devices which include specific hardware resources devoted to the IEE1588 functionalities. Unfortunately, this is not the approach followed in most of the large number of applications available nowadays. Therefore, most solutions are based in software and use standard hardware network interfaces. This paper presents the development of a hardware module (GI2E) with IEEE1588 capabilities which includes USB, RS232, RS485 and CAN interfaces. This permits to integrate any DAQ element that uses these interfaces in dDAQ systems in an efficient and simple way. The module has been developed with Motorola's Coldfire MCF5234 processor and National Semiconductors's PHY DP83640T, providing it with the possibility to implement the PTP protocol of IEEE1588 by hardware, and therefore increasing its performance over other implementations based in software. To facilitate the integration of the dDAQ system in control and measurement networks the module includes a basic Input/Output Controller (IOC) functionality of the Experimental Physics and Industrial Control System (EPICS) architecture. The paper discusses the implementation details of this module and presents its applications in advanced dDAQ applications in the fusion community
Data reduction in the ITMS system through a data acquisition model with self-adaptive sampling rate
Long pulse or steady state operation of fusion experiments require data acquisition and processing systems that reduce the volume of data involved. The availability of self-adaptive sampling rate systems and the use of real-time lossless data compression techniques can help solve these problems. The former is important for continuous adaptation of sampling frequency for experimental requirements. The latter allows the maintenance of continuous digitization under limited memory conditions. This can be achieved by permanent transmission of compressed data to other systems. The compacted transfer ensures the use of minimum bandwidth. This paper presents an implementation based on intelligent test and measurement system (ITMS), a data acquisition system architecture with multiprocessing capabilities that permits it to adapt the system’s sampling frequency throughout the experiment. The sampling rate can be controlled depending on the experiment’s specific requirements by using an external dc voltage signal or by defining user events through software. The system takes advantage of the high processing capabilities of the ITMS platform to implement a data reduction mechanism based in lossless data compression algorithms which are themselves based in periodic deltas
Nonlinear Interaction of Transversal Modes in a CO2 Laser
We show the possibility of achieving experimentally a Takens-Bogdanov
bifurcation for the nonlinear interaction of two transverse modes ()
in a laser. The system has a basic O(2) symmetry which is perturbed by
some symmetry-breaking effects that still preserve the symmetry. The
pattern dynamics near this codimension two bifurcation under such symmetries is
described. This dynamics changes drastically when the laser properties are
modified.Comment: 16 pages, 0 figure
Autopistas de la información. Aplicación en cirugía ortopédica
El término autopistas de información describe los servicios de telecomunicaciones
que estarán disponibles dentro de 10-15 años. El embrión de estas autopistas es Internet. Internet
ofrece 2 clases de servicios: a) comunicación entre usuarios de todo el mundo, y b) acceso a
servicios de información. En el primer grupo de estos servicios encontramos el correo electrónico
y los grupos de discusión. En el segundo podemos encontrar servicios como logon remoto,
transferencia de ficheros, Gopher o WWW. Describimos cada uno de estos servicios y su aplicación
a la ortopedia.Information highway describes the telecomunication services will be working in
the next 10-15 years. The embryo of this highway is Internet. Internet offers two kinds of services:
a) communication between users around the worid, and b) access to information services. In the
first group of this services we can find electronic mail and news group. In the second group we
can find services such as telnet, file transfer, Gopher and World Wide Web. We describe each of
this kind of services and their applications in orthopaedic surgery
Event Recognition Using Signal Spectrograms in Long Pulse Experiments
As discharge duration increases, real-time complex analysis of the signal becomes more important. In this context, data acquisition and processing systems must provide models for designing experiments which use event oriented plasma control. One example of advanced data analysis is signal classification. The off-line statistical analysis of a large number of discharges provides information to develop algorithms for the determination of the plasma parameters from measurements of magnetohydrodinamic waves, for example, to detect density fluctuations induced by the Alfvén cascades using morphological patterns. The need to apply different algorithms to the signals and to address different processing algorithms using the previous results necessitates the use of an event-based experiment. The Intelligent Test and Measurement System platform is an example of architecture designed to implement distributed data acquisition and real-time processing systems. The processing algorithm sequence is modeled using an event-based paradigm. The adaptive capacity of this model is based on the logic defined by the use of state machines in SCXML. The Intelligent Test and Measurement System platform mixes a local multiprocessing model with a distributed deployment of services based on Jini
Next-to-Minimal Supersymmetric Model Higgs Scenarios for Partially Universal GUT Scale Boundary Conditions
We examine the extent to which it is possible to realize the NMSSM "ideal
Higgs" models espoused in several papers by Gunion et al in the context of
partially universal GUT scale boundary conditions. To this end we use the
powerful methodology of nested sampling. We pay particular attention to whether
ideal-Higgs-like points not only pass LEP constraints but are also acceptable
in terms of the numerous constraints now available, including those from the
Tevatron and -factory data, and the relic density .
In general for this particular methodology and range of parameters chosen, very
few points corresponding to said previous studies were found, and those that
were found were at best away from the preferred relic density value.
Instead, there exist a class of points, which combine a mostly singlet-like
Higgs with a mostly singlino-like neutralino coannihilating with the lightest
stau, that are able to effectively pass all implemented constraints in the
region . It seems that the spin-independent direct detection cross
section acts as a key discriminator between ideal Higgs points and the hard to
detect singlino-like points.Comment: 22 pages, 15 figure
Statistical Complexity and Nontrivial Collective Behavior in Electroencephalografic Signals
We calculate a measure of statistical complexity from the global dynamics of
electroencephalographic (EEG) signals from healthy subjects and epileptic
patients, and are able to stablish a criterion to characterize the collective
behavior in both groups of individuals. It is found that the collective
dynamics of EEG signals possess relative higher values of complexity for
healthy subjects in comparison to that for epileptic patients. To interpret
these results, we propose a model of a network of coupled chaotic maps where we
calculate the complexity as a function of a parameter and relate this measure
with the emergence of nontrivial collective behavior in the system. Our results
show that the presence of nontrivial collective behavior is associated to high
values of complexity; thus suggesting that similar dynamical collective process
may take place in the human brain. Our findings also suggest that epilepsy is a
degenerative illness related to the loss of complexity in the brain.Comment: 13 pages, 3 figure
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