The application of non-orthogonal multiple access in wireless powered communication networks

This work investigates the application of non-orthogonal multiple access (NOMA) scheme for the uplink of wireless powered communication networks (WPCN). We maximize the sum rate by jointly designing of the time allocation, the downlink energy beamforming and receiver beamforming. To solve this nonconvex problem, a method of two stages optimization is proposed. In the first stage, we apply the series approximations to obtain the optimal energy beamforming and receive beamforming with fixed time allocation. In the second stage, one-dimensional search is considered to obtain the optimal time allocation. For the approximation part, successive convex approximation (SCA) method is used to convert a mixed integer non-linear program into its convex approximation problem. The numerical results illustrate that the proposed algorithm converges to the local optimum solution and the proposed scheme outperforms the fixed time allocation scheme and orthogonal multiple access (OMA)

Beamforming optimization for full-duplex cooperative cognitive radio networks

This paper considers the problem of beamforming optimization in a cognitive cooperative energy harvesting network, in which the secondary transmitter (ST) harvests energy from the primary transmitter (PT) and relays the information for the primary user (PU) with amplify-and-forward (AF) relay protocol. When the channel of the primary system is affected with deep fading or shadowing effects, the ST can assist the primary information transmission. It is particularly useful to employ the energy harvesting protocol to avoid that the ST does not have enough energy to assist the PU. Based on the self-energy recycling relay protocol, we study the beamforming optimization problem. We develop a semidefinite programming (SDP) relaxation method to solve the proposed problem. We also use SDP and one-dimension (1-D) optimization to solve the beamforming optimization based on a time-switching relaying protocol (TSR) as a benchmark. The simulation results are presented to verify that the self-energy recycling protocol achieves a significant rate gain compared to the TSR protocol and the power-splitting relaying (PSR) protocol

Eriocitrin alleviates sevoflurane-induced cytotoxicity in HT22 cells via Nrf2 pathway

Purpose: To investigate the effect of eriocitrin on sevoflurane-induced neurotoxicity in mice.Methods: Mouse hippocampal neurons (HT22) were exposed to different concentrations of sevoflurane for 6 h and then incubated with different concentrations of eriocitrin for another 24 h. Cell viability was determined by CCK8 assay, while fluorescence intensity of dichlorodihydrofluorescein was used to evaluate reactive oxygen species. Enzyme linked immunosorbent assay (ELISA) was used to determine oxidative stress, and cellular apoptosis was determined by flow cytometry.Results: Sevoflurane exposure decreased HT22 cell viability, whereas incubation with eriocitrin increased viability of sevoflurane-treated HT22 cells (p < 0.05). Sevoflurane-induced increase in dichlorodihydrofluorescein fluorescence intensity was reduced by eriocitrin, but eriocitrin attenuated sevoflurane-induced increase in malondialdehyde, superoxide dismutase, and glutathione peroxidase in HT22 cells. Cell apoptosis increased after sevoflurane exposure, and eriocitrin suppressed apoptosis in sevoflurane-treated HT22 cells through downregulation of cleaved caspase-3 and cleaved caspase-9 (p< 0.05). Eriocitrin incubation enhanced protein expression of nuclear factor E2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1), and NAD(P)H quinone dehydrogenase 1 (NQO1) in sevoflurane-treated HT22 cells (p < 0.05).Conclusion: Eriocitrin ameliorates sevoflurane-induced oxidative stress and inflammatory response in HT22 cells via activation of Nrf2/HO-1/NQO1 signaling. Thus, agent may be useful in the treatment of sevoflurane-induced toxicity, but in vivo studies are required to buttress this

Enhancing aerobic digestion of full-scale waste activated sludge using free nitrous acid pre-treatment

Aerobic digestion is one of the mainstream technologies for waste activated sludge (WAS) reduction and stabilization prior to disposal, but its effectiveness is limited by the poor degradation of WAS. This study presents a novel strategy based on free nitrous acid (FNA i.e. HNO2) pre-treatment to enhance full-scale WAS degradation in aerobic digestion. The full-scale WAS was subject to FNA treatment at 2.0 mg HNO2-N per L for 24 h. The degradation of the FNA-treated WAS was then compared to that of the same WAS without FNA pre-treatment by aerobically digesting the WAS with a full-scale activated sludge for 14 days. Approximately 50% of the FNA-treated WAS was degraded during the 14 day aerobic digestion compared to 32% achieved with the untreated WAS. The inorganic nitrogen production (originating from breakdown of WAS) from the FNA-treated WAS was 43 mg N per g of mixed liquor volatile suspended solids (MLVSS) in the 14 day aerobic digestion, whereas its production from the untreated WAS was only 29 mg N per g of MLVSS, confirming the effectiveness of the FNA pre-treatment in enhancing aerobic digestion of full-scale WAS. Economic analysis showed that the FNA pre-treatment method was economically attractive, saving a cost of %-15 500-64 500 per year depending on WAS disposal cost in a treatment plant with a population equivalent of 80 000