5,951 research outputs found
Stream bundle management layer for optimum management of co-existing telemedicine traffic streams under varying channel conditions in heterogeneous networks.
Heterogeneous networks facilitate easy and cost-effective penetration of medical advice in both rural and urban areas. However, disparate characteristics of different wireless networks lead to noticeable variations in network conditions when users roam among them e.g. during vertical handovers. Telemedicine traffic consists of a variety of real-time and non real-time traffic streams, each with a different set of Quality of Service requirements. This paper discusses the challenges and issues involved in the successful adaptation of heterogeneous networks by wireless telemedicine applications. We propose the development of a Smart Bundle Management (SBM) Layer for optimally managing co-existing traffic streams under varying channel conditions in a heterogeneous network. The SBM Layer acts as an interface between the applications and the underlying layers for maintaining a fair sharing of channel resources. Internal priority management algorithms are explained using Coloured Petri nets. This paper lays the foundation for the development of strategies for efficient management of co-existing traffic streams across varying channel conditions
Proactive policy management for heterogeneous networks
Context-awareness is a vital requirement of heterogeneous devices which allows them to predict future network conditions with sufficient accuracy. In this paper we present a proactive modelling-based approach for policy management which allows the mobile node to calculate Time Before Vertical Handover for open and closed environments.
The paper explains how the knowledge of this component can
improve the manner in which multi-class traffic streams are
allocated to available network channels. Simulation results
confirm the feasibility of the concept
Client-based SBM layer for predictive management of traffic flows in heterogeneous networks
In a heterogeneous networking environment, the knowledge of the time before a vertical handover (TBVH) for any network is vital in correctly assigning connections to available channels. In this paper, we introduce a predictive mathematical model for calculating the estimated TBVH component from available network parameters and discuss the different scenarios that arise based on a mobile host’s trajectory. We then introduce the concept of an intelligent Stream Bundle Management Layer (SBM) which consists of a set of policies for scheduling and mapping prioritised traffic streams on to available channels based on their priority, device mobility pattern and prevailing channel conditions. The layer is also responsible for the maintenance of connections during vertical handovers to avoid their forced termination
Proactive policy management using TBVH mechanism in heterogeneous networks.
In order to achieve seamless interoperability in
heterogeneous networking, it is vital to improve the
context-awareness of the mobile node (MN) so that it is
able to predict future network conditions with sufficient
accuracy. In this paper, we introduce a predictive
mathematical model for calculating the estimated Time
Before Vertical Handover (TBVH) component from
available network parameters. The model is practically
implemented in OPNET and our simulation results
confirm the validity of the concept. We then demonstrate
how the knowledge of TBVH along with other network
parameters can be applied by downward Quality of
Service management policies which bundle multi-class
traffic streams on to available network channels based
on application QoS, device mobility patterns and
prevailing channel conditions
Vestibulo-cerebellar disease impairs the central representation of self-orientation
Transformation of head-fixed otolith signals into a space-fixed frame of reference is essential for perception of self-orientation and ocular motor control. In monkeys the nodulus and ventral uvula of the vestibulo-cerebellum facilitate this transformation by computing an internal estimate of direction of gravity. These experimental findings motivated the hypothesis that degeneration of the vestibulo-cerebellum in humans alter perceptual and ocular motor functions that rely on accurate estimates of gravity, such as subjective visual vertical (SVV), static ocular counterroll (OCR), and gravity-dependent modulation of vertical ocular drifts. We assessed the SVV, OCR, and spontaneous vertical ocular drifts in 12 patients with chronic vestibulo-cerebellar disease and in 10 controls. Substantially increased variability in estimated SVV was noted in the patients. Furthermore, gravity-dependent modulation of spontaneous vertical ocular drifts along the pitch plane was significantly (p < 0.05) larger in the patients. However, the gain and variability of static OCR and errors in SVV were not significantly different. In conclusion, in chronic vestibulo-cerebellar disease SVV and OCR remain intact except for an abnormal variability in the perception of verticality and impaired stabilization of gaze mediated by the otoliths. These findings suggest that OCR and perceived vertical are relatively independent from the cerebellum unless there is a cerebellar imbalance like an acute unilateral cerebellar stroke. The increased trial-to-trial SVV variability may be a general feature of cerebellar disease since a function of the cerebellum may be to compensate for such. SVV variability might be useful to monitor disease progression and treatment response in patients
Determinants of Outcome in Non-Septic Critically Ill Patients with Acute Kidney Injury on Continuous Venovenous Hemofiltration
Background/Aims: In view of ongoing controversy, we wished to study whether patient characteristics and/or continuous venovenous hemofiltration (CVVH) characteristics contribute to the outcome of non-septic critically ill patients with acute kidney injury (AKI). Methods: We retrospectively studied 102 consecutive patients in the intensive care unit (ICU) with non-septic AKI needing CVVH. Patient and CVVH characteristics were evaluated. Primary outcome was mortality up to day 28 after CVVH initiation. Results: Forty-four patients (43%) died during the 28-day period after the start of CVVH. In univariate analyses, non-survivors had more often a cardiovascular reason for ICU admission, greater disease acuity/severity and organ failure, lower initial creatinine levels, less use of heparin and more use of bicarbonate-based substitution fluid. The latter two can be attributed to high lactate levels and bleeding tendency in non-survivors necessitating withholding lactate-buffered fluid and heparin, respectively, according to our clinical protocol. In multivariate analyses, mortality was predicted by disease severity, use of bicarbonate-based fluids and lack of heparin, while initial creatinine and CVVH dose did not contribute. Conclusion: The outcome of non-septic AKI in need of CVVH is more likely to be determined by underlying or concurrent, acute and severe disease rather than by CVVH characteristics, including timing and dose
Stability analysis of surface ion traps
Motivated by recent developments in ion trap design and fabrication, we
investigate the stability of ion motion in asymmetrical, planar versions of the
classic Paul trap. The equations of motion of an ion in such a trap are
generally coupled due to a nonzero relative angle between the
principal axes of RF and DC fields, invalidating the assumptions behind the
standard stability analysis for symmetric Paul traps. We obtain stability
diagrams for the coupled system for various values of , generalizing
the standard - stability diagrams. We use multi-scale perturbation theory
to obtain approximate formulas for the boundaries of the primary stability
region and obtain some of the stability boundaries independently by using the
method of infinite determinants. We cross-check the consistency of the results
of these methods. Our results show that while the primary stability region is
quite robust to changes in , a secondary stability region is highly
variable, joining the primary stability region at the special case of
, which results in a significantly enlarged stability region
for this particular angle. We conclude that while the stability diagrams for
classical, symmetric Paul traps are not entirely accurate for asymmetric
surface traps (or for other types of traps with a relative angle between the RF
and DC axes), they are safe in the sense that operating conditions deemed
stable according to standard stability plots are in fact stable for asymmetric
traps, as well. By ignoring the coupling in the equations, one only
underestimates the size of the primary stability region
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