This paper investigates the simultaneous wireless information and power transfer (SWIPT) in cooperative relay networks, where a relay harvests energy from the radio frequency (RF) signals transmitted ...by a source and then uses the harvested energy to assist the information transmission from the source to its destination. Both source and relay transmissions use rateless codes (RCs), which allow the destination to employ any of the two information receiving strategies, i.e., the mutual information accumulation (IA) and the energy accumulation (EA). The SWIPT-enabled relay employs three different SWIPT receiver architectures, the ideal receiver, and two practical receivers (i.e., the power splitting (PS) receiver and the time switch (TS) receiver). Accordingly, three relaying protocols, namely, the ideal protocol, PS protocol, and TS protocol, are presented. To explore the system performance limits with these three protocols, optimization problems are formulated to maximize their achievable information rates. For the ideal protocol, explicit expressions of the optimal solutions are derived. For the PS protocol, a linear-search algorithm is designed to solve the nonconvex problems. For the TS protocol, two solving methods are presented. Numerical experiments are carried out to validate our analysis and algorithms, which show that, with the same SWIPT receiver, the IA-based system outperforms the EA-based system, whereas with the same information receiving strategy, the PS protocol outperforms the TS protocol. Moreover, compared with nonrateless-coded systems, the proposed protocols exhibit considerable performance gains. Moreover, the effects of the relay position on system performance are also discussed, which provides insights on SWIPT-enabled relay systems.
Free-space optical (FSO) communication systems are negatively affected by two physical phenomenon, namely, scintillation due to atmospheric turbulence and pointing errors. To quantify the effect of ...these two factors on FSO system performance, we need an effective mathematical model for them. In this paper, we propose and study a generalized pointing error model based on the Beckmann distribution. We then derive a generic expression of the asymptotic capacity of FSO systems under the joint impact of turbulence and generalized pointing error impairments. Finally, the asymptotic channel capacity formula is extended to quantify the FSO systems performance with selection and switched-and-stay diversity.
In this letter, we consider a dual-hop heterogeneous visible light communication (VLC)/radio frequency (RF) communication system to extend the coverage of VLC systems. Besides detecting the ...information over VLC link, the relay is able to harvest energy from the first-hop VLC link, by extracting the direct current component of the received optical signal, and uses the harvested energy to retransmit the data to a mobile terminal over the second-hop RF link. We investigate the optimal design of the hybrid system in terms of data rate maximization.
In this letter, we propose an UAV-based relaying system with energy harvesting functionality. In particular, we assume that this system is operated in urban communication environments, where the ...channel between the UAV and the land destination is modeled as shadowed-Rician fading or shadowed-Rayleigh fading. Based on this setting, outage probability analysis for different urban environment parameters is derived. Finally, Monte Carlo simulations are conducted to verify the accuracy of our analytical results.
This study uses spark plasma sintering (SPS) to prepare graphene nanoplatelet (GNP)-reinforced titanium matrix composite materials. Heat treatment is used during rolling and annealing (R&A) to ...enhance the interfacial bonding strength between the graphene and titanium crystal grains, uniformly disperse the graphene and refine the grains. Studies have shown that the relative density (RD) of composites increased from 84% to 98% as the processing temperature increased from 600 °C to 1100 °C. Under the optimized plasma sintering process parameters, the best solid-phase reaction temperature is 850 °C, and the tensile strength at room temperature after R&A can reach 1206 MPa for 0.3 wt% GNP titanium matrix composites; this result represents an increase of 46% compared with pure titanium (PTi) under the same conditions. The reduction of area (ψ) of the 0.3 wt% GNP titanium matrix composite can reach 48%. The strengthening mechanisms include composite, grain and second-phase strengthening, wherein composite strengthening is the controlling factor. Additionally, the strength of composites at 1100 °C also increases, but ψ remains a lower level. The formation of nanocarbide particle layers causes a significant reduction in ψ.
Display omitted
•The prepared graphene and the CPTi were used to create composites by SPS.•The microhardness in the ROD was the lowest among the three directions After R&A.•After R&A, the 0.3 wt% graphene composites at 850 °C possessed excellent mechanical properties.•Graphene reacted with Ti to form a large amount of titanium carbide particle layers at 1100 °C.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this paper, we consider an unmanned aerial vehicle (UAV)-enabled decode-and-forward (DF) relay network. In order to mitigate the on-board energy limitation of the UAV, the source to UAV link ...employs simultaneous information and power transfer (SWIPT) with power splitting (PS) protocol. Thereby, the information forwarding at the UAV will be solely powered by its harvested energy. We aim to maximize the aggregate end-to-end throughput by optimizing the transmit power of the source and UAV, PS ratio, and UAV trajectory. Since the optimization variables are closely coupled, the formulated problem is non-convex. To tackle this issue, we adopt a block coordinate descent method to divide the optimization variables into two blocks, each of which is alternately optimized while fixing the other. We optimize the transmit power, PS ratio, and UAV trajectory by applying the Lagrange duality and the sequential convex programming algorithm, respectively. Simulation results show that our proposed design considerably outperforms the conventional baseline schemes.
Obesity is associated with biological dysfunction in skeletal muscle. As a condition of obesity accompanied by muscle mass loss and physical dysfunction, sarcopenic obesity (SO) has become a novel ...public health problem. Human fibroblast growth factor 19 (FGF19) plays a therapeutic role in metabolic diseases. However, the protective effects of FGF19 on skeletal muscle in obesity and SO are still not completely understood. Our results showed that FGF19 administration improved muscle loss and grip strength in young and aged mice fed a high‐fat diet (HFD). Increases in muscle atrophy markers (FOXO‐3, Atrogin‐1, MuRF‐1) were abrogated by FGF19 in palmitic acid (PA)‐treated C2C12 myotubes and in the skeletal muscle of HFD‐fed mice. FGF19 not only reduced HFD‐induced body weight gain, excessive lipid accumulation and hyperlipidaemia but also promoted energy expenditure (PGC‐1α, UCP‐1, PPAR‐γ) in brown adipose tissue (BAT). FGF19 treatment restored PA‐ and HFD‐induced hyperglycaemia, impaired glucose tolerance and insulin resistance (IRS‐1, GLUT‐4) and mitigated the PA‐ and HFD‐induced decrease in FNDC‐5/irisin expression. However, these beneficial effects of FGF19 on skeletal muscle were abolished by inhibiting AMPK, SIRT‐1 and PGC‐1α expression. Taken together, this study suggests that FGF19 protects skeletal muscle against obesity‐induced muscle atrophy, metabolic derangement and abnormal irisin secretion partially through the AMPK/SIRT‐1/PGC‐α signalling pathway, which might be a potential therapeutic target for obesity and SO.
Full text
Available for:
FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
We study the optimum design of an energy harvesting relay for two-way decode-and-forward (DF) relay networks. In the networks, the relay harvests energy as well as decodes information using the ...received signal from two sources with power splitting relaying (PSR) and time switching relaying (TSR) strategies. Since the two-way relay network has two opposite traffic flows, it can be considered as a special case of multi-user systems. Applying the max-min criterion for fairness and max-sum criterion for maximum resource utilization, we optimize the operations of the energy harvesting relay. Specifically, considering the transmission rate constraints of individual hops, we derive optimum power splitting coefficients and optimum time switching coefficients, respectively, for PSR-based and TSR-based networks under both criterions, and analytically calculate the resulting maximum transmission rates. Numerical results confirm that our analyses exactly match with exhaustive search simulations. The obtained optimum coefficients are given in closed-form, therefore, they can be easily adopted in simple two-way relay networks with limited computational power such as sensor/Internet of Things (IoT) networks and can help two-way DF relay networks.
In this paper, we study an unmanned aerial vehicle (UAV)-assisted relaying communication system, where a ground base station (GBS) intends to send information to a legitimate ground user (Bob) with ...the help of a UAV relay, in the presence of a passive ground eavesdropper (Eve). In particular, assuming an urban operating environment, we analyze and derive the closed-form approximation of the intercept probability and the ergodic secrecy rate. Through analytical and numerical results, we examine the effect of different system parameters on secrecy performance.
Hybrid free-space optical (FSO)/radio-frequency (RF) systems have emerged as a promising solution for high-data-rate wireless transmission. We present and analyze a transmission scheme for the hybrid ...FSO/RF communication system based on adaptive combining. Specifically, only FSO link is active as long as the instantaneous signal-to-noise ratio (SNR) at the FSO receiver is above a certain threshold level. When it falls below this threshold level, the RF link is activated along with the FSO link and the signals from the two links are combined at the receiver using a dual-branch maximal ratio combiner. Novel analytical expression for the cumulative distribution function (CDF) of the received SNR for the proposed hybrid system is obtained. This CDF expression is used to study the system outage performance. Numerical examples are presented to compare the outage performance of the proposed hybrid FSO/RF system with that of the FSO-only and RF-only systems.
PDF
