3,346 research outputs found
Power vs. Spectrum 2-D Sensing in Energy Harvesting Cognitive Radio Networks
Energy harvester based cognitive radio is a promising solution to address the
shortage of both spectrum and energy. Since the spectrum access and power
consumption patterns are interdependent, and the power value harvested from
certain environmental sources are spatially correlated, the new power dimension
could provide additional information to enhance the spectrum sensing accuracy.
In this paper, the Markovian behavior of the primary users is considered, based
on which we adopt a hidden input Markov model to specify the primary vs.
secondary dynamics in the system. Accordingly, we propose a 2-D spectrum and
power (harvested) sensing scheme to improve the primary user detection
performance, which is also capable of estimating the primary transmit power
level. Theoretical and simulated results demonstrate the effectiveness of the
proposed scheme, in term of the performance gain achieved by considering the
new power dimension. To the best of our knowledge, this is the first work to
jointly consider the spectrum and power dimensions for the cognitive primary
user detection problem
Design guidelines for spatial modulation
A new class of low-complexity, yet energyefficient Multiple-Input Multiple-Output (MIMO) transmission techniques, namely the family of Spatial Modulation (SM) aided MIMOs (SM-MIMO) has emerged. These systems are capable of exploiting the spatial dimensions (i.e. the antenna indices) as an additional dimension invoked for transmitting information, apart from the traditional Amplitude and Phase Modulation (APM). SM is capable of efficiently operating in diverse MIMO configurations in the context of future communication systems. It constitutes a promising transmission candidate for large-scale MIMO design and for the indoor optical wireless communication whilst relying on a single-Radio Frequency (RF) chain. Moreover, SM may also be viewed as an entirely new hybrid modulation scheme, which is still in its infancy. This paper aims for providing a general survey of the SM design framework as well as of its intrinsic limits. In particular, we focus our attention on the associated transceiver design, on spatial constellation optimization, on link adaptation techniques, on distributed/ cooperative protocol design issues, and on their meritorious variants
Existence of positive solution for a third-order three-point BVP with sign-changing Green's function
By using the Guo-Krasnoselskii fixed point theorem, we investigate the following third-order three-point boundary value problem
where and . The emphasis is mainly that although the corresponding Green's function is sign-changing, the solution obtained is still positive
Acute Exercise Induced Mitochondrial H 2
Exercise induced skeletal muscle phenotype change involves a complex interplay between signaling pathways and downstream regulators. This study aims to investigate the effect of acute exercise on mitochondrial H2O2 production and its association with p66Shc, FOXO3a, and antioxidant enzymes. Male ICR/CD-1 mice were subjected to an acute exercise. Muscle tissues (gastrocnemius and quadriceps femoris) were taken after exercise to measure mitochondrial H2O2 content, expression of p66Shc and FOXO3a, and the activity of antioxidant enzymes. The results showed that acute exercise significantly increased mitochondrial H2O2 content and expressions of p66Shc and FOXO3a in a time-dependent manner, with a linear correlation between the increase in H2O2 content and p66Shc or FOXO3a expression. The activity of mitochondrial catalase was slightly reduced in the 90 min exercise group, but it was significantly higher in groups with 120 and 150 min exercise compared to that of 90 min exercise group. The activity of SOD was not significantly affected. The results indicate that acute exercise increases mitochondrial H2O2 production in the skeletal muscle, which is associated with the upregulation of p66Shc and FOXO3a. The association of p66Shc and FOXO3a signaling with exercise induced H2O2 generation may play a role in regulating cellular oxidative stress during acute exercise
Observation of fourfold Dirac nodal line semimetal and its unconventional surface responses in sonic crystals
Three-dimensional nodal line semimetals (NLSMs) provide remarkable importance
for both enrich topological physics and wave management. However, NLSMs
realized in acoustic systems are twofold bands degenerate, which are called
Weyl NLSMs. Here, we first report on the experimental observation of novel
Dirac NLSMs with fourfold degenerate in sonic crystals. We reveal that the
topological properties of the Dirac NLSMs are entirely different than that of
the conventional Weyl NLSMs. The Berry phase related to the Dirac nodal line
(DNL) is 2{\pi}, which results in the surface responses of the Dirac NLSMs with
two radically different situations: a torus surface state occupying the entire
surface Brillouin zone (SBZ) and without any surface state in the SBZ. We
further reveal that topological surface arcs caused by DNL can change from open
to closed contours. The findings of Dirac NLSMs and their unique surface
response may provoke exciting frontiers for flexible manipulation of acoustic
surface waves.Comment: 6 pages, 4 figure
Probing Primordial Gravitational Waves: Ali CMB Polarization Telescope
In this paper, we will give a general introduction to the project of Ali CMB
Polarization Telescope (AliCPT), which is a Sino-US joint project led by the
Institute of High Energy Physics (IHEP) and has involved many different
institutes in China. It is the first ground-based Cosmic Microwave Background
(CMB) polarization experiment in China and an integral part of China's
Gravitational Waves Program. The main scientific goal of AliCPT project is to
probe the primordial gravitational waves (PGWs) originated from the very early
Universe.
The AliCPT project includes two stages. The first stage referred to as
AliCPT-1, is to build a telescope in the Ali region of Tibet with an altitude
of 5,250 meters. Once completed, it will be the worldwide highest ground-based
CMB observatory and open a new window for probing PGWs in northern hemisphere.
AliCPT-1 telescope is designed to have about 7,000 TES detectors at 90GHz and
150GHz. The second stage is to have a more sensitive telescope (AliCPT-2) with
the number of detectors more than 20,000.
Our simulations show that AliCPT will improve the current constraint on the
tensor-to-scalar ratio by one order of magnitude with 3 years' observation.
Besides the PGWs, the AliCPT will also enable a precise measurement on the CMB
rotation angle and provide a precise test on the CPT symmetry. We show 3 years'
observation will improve the current limit by two order of magnitude.Comment: 11 pages, 7 figures, 2 table
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