In this paper, we investigate optimal resource allocation in a power beacon-assisted wireless-powered communication network (PB-WPCN), which consists of a set of hybrid access point (AP)-source pairs ...and a power beacon (PB). Each source, which has no embedded power supply, first harvests energy from its associated AP and/or the PB in the downlink (DL) and then uses the harvested energy to transmit information to its AP in the uplink (UL). We consider both cooperative and non-cooperative scenarios based on whether the PB is cooperative with the APs or not. For the cooperative scenario, we formulate a social welfare maximization problem to maximize the weighted sum-throughput of all AP-source pairs, which is subsequently solved by a water-filling based distributed algorithm. In the non-cooperative scenario, all the APs and the PB are assumed to be rational and self-interested such that incentives from each AP are needed for the PB to provide wireless charging service. We then formulate an auction game and propose an auction based distributed algorithm by considering the PB as the auctioneer and the APs as the bidders. Finally, numerical results are performed to validate the convergence of both the proposed algorithms and demonstrate the impacts of various system parameters.
Abstract
Regenerable nanozymes with high catalytic stability and sustainability are promising substitutes for naturally-occurring enzymes but are limited by insufficient and non-selective catalytic ...activities. Herein, we developed single-atom nanozymes of RhN
4
, VN
4
, and Fe-Cu-N
6
with catalytic activities surpassing natural enzymes. Notably, Rh/VN
4
preferably forms an Rh/V-O-N
4
active center to decrease reaction energy barriers and mediates a “two-sided oxygen-linked” reaction path, showing 4 and 5-fold higher affinities in peroxidase-like activity than the FeN
4
and natural horseradish peroxidase. Furthermore, RhN
4
presents a 20-fold improved affinity in the catalase-like activity compared to the natural catalase; Fe-Cu-N
6
displays selectivity towards the superoxide dismutase-like activity; VN
4
favors a 7-fold higher glutathione peroxidase-like activity than the natural glutathione peroxidase. Bioactive sutures with Rh/VN
4
show recyclable catalytic features without apparent decay in 1 month and accelerate the scalp healing from brain trauma by promoting the vascular endothelial growth factor, regulating the immune cells like macrophages, and diminishing inflammation.
Intuitively, higher intelligence might be assumed to correspond to more efficient information transfer in the brain, but no direct evidence has been reported from the perspective of brain networks. ...In this study, we performed extensive analyses to test the hypothesis that individual differences in intelligence are associated with brain structural organization, and in particular that higher scores on intelligence tests are related to greater global efficiency of the brain anatomical network. We constructed binary and weighted brain anatomical networks in each of 79 healthy young adults utilizing diffusion tensor tractography and calculated topological properties of the networks using a graph theoretical method. Based on their IQ test scores, all subjects were divided into general and high intelligence groups and significantly higher global efficiencies were found in the networks of the latter group. Moreover, we showed significant correlations between IQ scores and network properties across all subjects while controlling for age and gender. Specifically, higher intelligence scores corresponded to a shorter characteristic path length and a higher global efficiency of the networks, indicating a more efficient parallel information transfer in the brain. The results were consistently observed not only in the binary but also in the weighted networks, which together provide convergent evidence for our hypothesis. Our findings suggest that the efficiency of brain structural organization may be an important biological basis for intelligence.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Emerging artificial enzymes with reprogrammed and augmented catalytic activity and substrate selectivity have long been pursued with sustained efforts. The majority of current candidates have rather ...poor catalytic activity compared with natural molecules. To tackle this limitation, we design artificial enzymes based on a structurally well-defined Au
cluster, namely clusterzymes, which are endowed with intrinsic high catalytic activity and selectivity driven by single-atom substitutions with modulated bond lengths. Au
Cu
and Au
Cd
clusterzymes exhibit 137 and 160 times higher antioxidant capacities than natural trolox, respectively. Meanwhile, the clusterzymes demonstrate preferential enzyme-mimicking catalytic activities, with Au
, Au
Cu
and Au
Cd
displaying compelling selectivity in glutathione peroxidase-like (GPx-like), catalase-like (CAT-like) and superoxide dismutase-like (SOD-like) activities, respectively. Au
Cu
decreases peroxide in injured brain via catalytic reactions, while Au
Cd
preferentially uses superoxide and nitrogenous signal molecules as substrates, and significantly decreases inflammation factors, indicative of an important role in mitigating neuroinflammation.
This letter investigates a joint antenna selection (AS) problem for a MIMO cognitive radio-inspired non-orthogonal multiple access network. In particular, a new computationally efficient joint AS ...algorithm, namely subset-based joint AS (SJ-AS), is proposed to maximize the signal-to-noise ratio of the secondary user under the condition that the quality of service of the primary user is satisfied. The asymptotic closed-form expression of the outage performance for SJ-AS is derived, and the minimal outage probability achieved by SJ-AS among all possible joint AS schemes is proved. The provided numerical results demonstrate the superior performance of the proposed scheme.
In recent years, underwater visible light communication (UVLC) has become a potential wireless carrier candidate for signal transmission in highly critical, unknown, and acrimonious water mediums ...such as oceans. Unfortunately, the oceans are the least explored reservoirs in oceanogeographical history. However, natural disasters have aroused significant interest in observing and monitoring oceanic environments for the last couple of decades. Therefore, UVLC has drawn attention as a reliable digital carrier and claims a futuristic optical media in the wireless communication domain. Counterparts of traditional communications, the green, clean, and safe UVLC support high capacity data-rate and bandwidth with minimal delay. Nevertheless, the deployment of UVLC is challenging rather than terrestrial basis communication over long ranges. In addition, UVLC systems have severe signal attenuation and strong turbulence channel conditions. Due to the fact that, this study provides an exhaustive and comprehensive survey of recent advancements in UVLC implementations to cope with the optical signal propagation issues. In this regard, a wide detailed summary and future perspectives of underwater optical signaling towards 5G and beyond (5GB) networks along with the current project schemes, channel impairments, various optical signal modulation techniques, underwater sensor network (UWSN) architectures with energy harvesting approaches, hybrid communication possibilities, and advancements of Internet of underwater things (IoUTs) are concluded in this research.
The recent significant progress in realizing FD systems has opened up a promising avenue for improving quality of service and quality of experience in future wireless networks. There is an urgent ...need to address the diverse set of challenges regarding different aspects of FD network design, theory, and development. In addition to the self-interference cancellation signal processing algorithms, network protocols such as resource management are also essential in the practical design and implementation of FD wireless networks. This article aims to present the latest development and future directions of resource allocation in different full duplex systems by exploring the network resources in different domains, including power, space, frequency, and device dimensions. Four representative application scenarios are considered: FD MIMO networks, FD cooperative networks, FD OFDMA cellular networks, and FD heterogeneous networks. Resource management problems and novel algorithms in these systems are presented, and key open research directions are discussed.
Cell-free system is an efficient solution to eliminate inter-cell interference by serving users without cell boundaries. To further improve the spectrum efficiency, in this letter, we consider a ...reconfigurable intelligent surface (RIS) aided cell-free MIMO system. Multiple RISs are employed to create favorable propagation conditions via configurable reflection from the BS to users. Benefited from multiple transmission paths the spatial resources can be better utilized. We develop a hybrid beamforming (HBF) scheme consisting of the digital beamforming at the BS and the RIS-based beamforming. A sum rate optimization (SRO) problem is formulated and an iterative algorithm is designed to solve this problem. Simulation results show that the proposed system can achieve a significant performance gain compared to conventional single cell systems without RISs and distributed antenna systems.
We propose a novel random access (RA) scheme with the quality of service (QoS) guarantees for machine-to-machine (M2M) communications. We consider a slotted uncoordinated data transmission period ...during which machine type communication (MTC) devices transmit over the same radio channel. Based on the latency requirements, MTC devices are divided into groups of different sizes, and the transmission frame is divided into sub-frames of different lengths. In each sub-frame, each group is assigned an access probability based on which an MTC device decides to transmit replicas of its packet or remain silent. The base station employs successive interference cancellation to recover all the superposed packets. We derive the closed-form expressions for the average probability of device resolution for each group, and we use these expressions to design the access probabilities. The accuracy of the expressions is validated through Monte Carlo simulations. We show that the designed access probabilities can guarantee the QoS requirements with high reliability and high energy efficiency. Finally, we show that RA can outperform standard coordinated access schemes as well as some of the recently proposed M2M access schemes for cellular networks.
MIMO systems with adaptive modulation Zhendong Zhou; Vucetic, B.; Dohler, M. ...
IEEE transactions on vehicular technology,
09/2005, Letnik:
54, Številka:
5
Journal Article
Recenzirano
Adaptive modulation (AM) schemes in multiple input multiple output (MIMO) systems with a perfect or imperfect channel state information (CSI) at both the transmitter and receiver were investigated. ...Under an average transmit power and instantaneous bit error rate (BER) constraint, the transmit parameters including the subchannel transmit power and/or spectral efficiency are optimally adapted in the spatial and/or temporal domain to maximize the average spectral efficiency (ASE). Two categories, the continuous rate and discrete rate, of adaptive systems were considered, where the derived asymptotic closed form expressions for the former provided much insight into the latter. Analytical and numerical results showed that a full multiplexing gain was achieved in variable rate variable power (VRVP) systems and variable rate (VR) systems. Variable power (VP) systems with unequal numbers of transmit and receive antennas also achieved the full multiplexing gain, unlike VP systems with equal number of transmit and receive antennas. The effect of CSI imperfection on the ASE and BER was evaluated for VR systems and closed form expressions for the ASE and BER were obtained. They prove to be a useful tool to assess the system performance without taking time consuming AM MIMO system simulations.
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