6,069 research outputs found
Automorphisms of abelian group extensions
Let be an abelian extension. The purpose of this
paper is to study the problem of extending automorphisms of and lifting
automorphisms of to certain automorphisms of .Comment: 11 page
Capacity Comparison between MIMO-NOMA and MIMO-OMA with Multiple Users in a Cluster
In this paper, the performance of multiple-input multiple-output
non-orthogonal multiple access (MIMO-NOMA) is investigated when multiple users
are grouped into a cluster. The superiority of MIMO-NOMA over MIMO orthogonal
multiple access (MIMO-OMA) in terms of both sum channel capacity and ergodic
sum capacity is proved analytically. Furthermore, it is demonstrated that the
more users are admitted to a cluster, the lower is the achieved sum rate, which
illustrates the tradeoff between the sum rate and maximum number of admitted
users. On this basis, a user admission scheme is proposed, which is optimal in
terms of both sum rate and number of admitted users when the
signal-to-interference-plus-noise ratio thresholds of the users are equal. When
these thresholds are different, the proposed scheme still achieves good
performance in balancing both criteria. Moreover, under certain conditions,it
maximizes the number of admitted users. In addition, the complexity of the
proposed scheme is linear to the number of users per cluster. Simulation
results verify the superiority of MIMO-NOMA over MIMO-OMA in terms of both sum
rate and user fairness, as well as the effectiveness of the proposed user
admission scheme.Comment: accepted IEEE Journal on Selected Topics in Communications, June
2017, Keywords: Non-orthogonal multiple access (NOMA), multiple-input
multiple-output (MIMO), channel capacity, sum rate, fairness, user admission,
power allocatio
An Iterative Cyclic Algorithm for Designing Vaccine Distribution Networks in Low and Middle-Income Countries
The World Health Organization's Expanded Programme on Immunization (WHO-EPI)
was developed to ensure that all children have access to common childhood
vaccinations. Unfortunately, because of inefficient distribution networks and
cost constraints, millions of children in many low and middle-income countries
still go without being vaccinated. In this paper, we formulate a mathematical
programming model for the design of a typical WHO-EPI network with the goal of
minimizing costs while providing the opportunity for universal coverage. Since
it is only possible to solve small versions of the model optimally, we describe
an iterative heuristic that cycles between solving restrictions of the original
problem and show that it can find very good solutions in reasonable time for
larger problems that are not directly solvable.Comment: International Joint Conference on Industrial Engineering and
Operations Management- ABEPRO-ADINGOR-IISE-AIM-ASEM (IJCIEOM 2019). Novi Sad,
Serbia, July 15-17t
A Two-Phase Power Allocation Scheme for CRNs Employing NOMA
In this paper, we consider the power allocation (PA) problem in cognitive
radio networks (CRNs) employing nonorthogonal multiple access (NOMA) technique.
Specifically, we aim to maximize the number of admitted secondary users (SUs)
and their throughput, without violating the interference tolerance threshold of
the primary users (PUs). This problem is divided into a two-phase PA process:
a) maximizing the number of admitted SUs; b) maximizing the minimum throughput
among the admitted SUs. To address the first phase, we apply a sequential and
iterative PA algorithm, which fully exploits the characteristics of the
NOMA-based system. Following this, the second phase is shown to be quasiconvex
and is optimally solved via the bisection method. Furthermore, we prove the
existence of a unique solution for the second phase and propose another PA
algorithm, which is also optimal and significantly reduces the complexity in
contrast with the bisection method. Simulation results verify the effectiveness
of the proposed two-phase PA scheme
Connection between accretion disk and superluminal radio jets and the role of radio plateau state in GRS 1915+105
We investigate the association between the accretion disk during radio
plateau state and the following superluminal relativistic radio jets with peak
intensity varies from 200 mJy to 1000 mJy observed over a period of five years
and present the evidences of direct accretion disc-jet connection in
microquasar GRS 1915+105. We have analysed RXTE PCA/HEXTE X-ray data and have
found that the accretion rate, , as inferred from the X-ray
flux, is very high during the radio plateaux. We suggest that the accretion
disk during the radio plateaux always associated with radiation-driven wind
which is manifested in the form of enhanced absorption column density for X-ray
and the depleted IR emission. We find that the wind density increases with the
accretion disk luminosity during the radio plateaux. The wind density is
similar to the density of the warm absorber proposed in extragalactic AGNs and
Quasars. We suggest a simple model for the origin of superluminal relativistic
jets. Finally, We discuss the implications of this work for galactic
microquasars and the extragalactic AGNs and Quasars.Comment: 9 pages, 6 Figures, Accepted for publication in Ap
Management of Traumatic Pseudoaneurysm of the Supraclinoid Internal Carotid Artery using Coil Embolization: A Case Report
Traumatic aneurysm of the internal carotid artery (ICA) occurs rarely, with an approximate incidence of 0.15% and 0.40% of total intracranial aneurysms. An interesting case of delayed presentation of pseudoaneurysm of the left ICA in a 61-year-old patient is reported here, who came to us for evaluation of blindness, proptosis, and ophthalmoparesis. This potentially life-threatening condition was successfully managed using coil embolization after complete evaluation and investigations
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