With the rapid development of applications with different use cases and service demands for edge network, network slicing is an emerging solution for satisfying service-oriented requirements, while ...the low earth orbit (LEO) satellite caching-assisted communication has been considered as one of the key elements for effective services. With limited resources at the edge of the radio access network (RAN), it is challenging to take advantage of the LEO content cache to joint allocation of communication, computing and caching space (3C) resources. To this end, we investigate the problem of resource slicing and scheduling of joint 3C resources in RAN edge scenario assisted by LEO content caching. A hierarchical resource slicing framework is proposed for dynamic allocation of multidimensional resources. The optimization variables are relaxed and the constraints are adjusted. The sequential quadratic programming (SQP) iteration algorithm is proposed as theoretical offline baseline. Due to its complex solving process and limited real-time performance, we incorporate Long Short-Term Memory (LSTM) into the Soft Actor-Critic (SAC) algorithm to aware extract the distribution characteristics of historical information and propose the deep reinforcement learning algorithm of LSTM-SAC. Meanwhile, the proportional priority based scheduling algorithm is employed in the intra-slice. Compared to SAC, TD3 and DDPG algorithms, the proposed algorithm is the closest to the theoretical value, improves the objective function by 6.95%, 9.52% and 11.52% respectively, which can significantly improve the system rate while satisfying the service level agreements.
The demand for various types of services is growing rapidly with the development of beyond 5G/6G networks, network slicing (NS) is considered as an effective technology to cope with the multiple ...services and large traffic demand. In this article, a NS resource allocation optimization algorithm based on multiactor-attention-critic (MAAC) joint with bidding is proposed to guarantee the service satisfaction rate (SSR) while increasing the profit of mobile virtual network operator (MVNO) in heterogeneous integrated networks. First, a pricing and bidding strategies are designed for users with different service requirements and service indexes, and the resource allocation is modeled to maximize the sum of utility of all MVNO subjected to MVNO's pricing and bandwidth constraints accordingly. Second, the optimization problem is analyzed based on the augment Lagrange method, relaxed and has been proved as a convex optimization, and then, the alternating direction multiplier method is adopted to obtain the theoretical upper bound with 32.047 of the network utility. Meanwhile, the gradient descent method with different learning rates is used to accelerate the convergence rate. Third, the MAAC-based algorithm is proposed and the resource allocation procedures are transformed into a partially observable Markov decision process, in which the interactions with multiagent environment are performed accurately. Finally, the simulation results indicate that the network utility of the proposed algorithm can be improved by 25.074% while ensuring the users' SSR. Compared with multiagent deep determination strategy gradient and dueling deep Q network, the network utility by the proposed algorithm can be improved by 6.265% and 39.791%, respectively, up to 27.664, which can be closest to the theoretical upper bound at the greatest extent.
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.
A combined heterotrophic-sulfur-autotrophic system (CHSAS) was established to simultaneously reduce perchlorate and nitrate in water. In this system, the OH− produced by the acetate heterotrophic ...part (H-part) could be neutralized with the H+ produced by the sulfur autotrophic part (S-part); thus, the pH of the final effluent could keep neutral. In addition, the S-part could further reduce the pollutants and residual carbon from the H-part to achieve a high performance. For 19.62 ± 0.30 mg/L ClO4− and 21.56 ± 0.83 mg/L NO3−-N in the influent, the operating parameters were optimal at a hydraulic retention time (HRT) of 1.0 h and an acetate concentration of 70 mg/L. The removal efficiency of ClO4− and NO3− reached 95.43% and 99.23%, without secondary pollution caused by residual organic carbon. It was also revealed that sulfur (S0) disproportionation can be inhibited by shortening the HRT and reducing the acetate dosage. The dominant heterotrophic and autotrophic bacteria were Thauera and Ferritrophicum, respectively, while Chlorobaculum was related to S0 disproportionation.
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•A CHSAS system was developed for perchlorate and nitrate removal.•Shortening HRT and reducing acetate dosage can inhibit S0 disproportionation.•The S-Part further degraded carbon source to eliminate secondary pollution.•The pH and alkalinity of the effluent could keep balance with influent.•Thauera and Ferritrophicum were dominant bacteria of H-part and S-part.
This study investigates the sulfur (S) disproportionation tendencies in a sulfur packed bed reactor for perchlorate bio-autotrophic reduction at different temperatures. The reactor was operated with ...over 99% efficiency for 21.00 ± 1.40 mg L−1 perchlorate removal when the hydraulic retention time (HRT) ranged from 12.00 h to 0.75 h at 27 ± 2 °C. When HRT was controlled at 1.00 h, the perchlorate removal efficiency was only 8 ± 1% as the temperature dropped to 6 ± 1 °C. The half-order model fit both perchlorate removal and S disproportionation reaction well. Compared with S disproportionation, the decrease of temperature had a greater influence on perchlorate reduction. As the temperature dropped from 27 ± 2 °C to 6 ± 1 °C, the 1/2K1/2v,R for perchlorate reduction decreased from 7.37 mg1/2 L−1/2 h−1 to 0.19 mg1/2 L−1/2 h−1. Meanwhile, the 1/2K1/2v,S for S disproportionation decreased from 3.04 mg1/2 L−1/2 h−1 to 1.96 mg1/2 L−1/2 h−1. The reaction activation energy of perchlorate reduction and S disproportionation was 120.28 kJ mol−1 and 13.44 kJ mol−1, respectively. The S disproportionation reaction proceeded remarkably at the beginning of the reduction, a longer HRT and higher temperature promoted S disproportionation, resulting in excessive sulfate generation and alkalinity consumption. Besides, the spatial distribution of the microbial communities and the dominant bacteria function under different HRTs was analyzed using high-throughput sequencing.
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•The acceleration of S disproportionation was discovered.•21.00 mg/L ClO4− was removed >99% at HRT 0.75 h (27 ± 2 °C).•1/2 kinetics model fit both perchlorate removal and S disproportionation well.•Spatial distribution of the microbial communities was analyzed.•Bacterial α and β diversity, and dominant genus was investigated.
A novel Moving-Bed Biofilm Reactor (MBBR), based on proton-exchange membrane electrolysis, was developed and tested for perchlorate transformation. The bacteria growing on the carrier in the cathode ...chamber could use in situ-generated hydrogen to reduce perchlorate to chloride via electrolysis; the resulting chloride ions and chloride ions in raw water were then oxidized into chlorine by anode reaction to disinfect the final effluent and improve water quality. For a ClO4− concentration of 10.00 ± 0.08 mg/L in the influent, at hydraulic retention times (HRTs) of 4.0, 2.0, and 1.5 h, the optimal applied currents (OACs) were 130, 240, and 270 mA, with a corresponding removal efficiencies of 99.90 ± 0.21, 96.70 ± 0.36, and 78.50 ± 0.24%, respectively. Active chlorine concentration was in the range of 0.063–0.096 mg/L, contributing to simultaneous electro-disinfection. Along the water flow direction, OH– generated by the cathode could be neutralized in the anode chamber; thus, the final effluent pH was kept a balance with the influent pH. Proteobacteria, Bacteroidetes, and Firmicutes were the dominant bacteria in the MBBR. The maximum value of current efficiency (13.32 ± 0.69%) was obtained at 100 mA and an HRT of 4.0 h, which was in accordance with the abundance of Thauera.
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•A novel MBBR based on membrane electrolysis was developed for ClO4− conversion.•The bioreduction and electro-disinfection occurred simultaneously in this system.•The H2 supply limiting and pH limiting tendency was related to the applied current.•The final effluent pH could keep balance with the influent.•The Thauera was the dominate PRB related to current efficiency.
•We develop a label-free SERS strategy toward milk contaminant analysis.•The Au@Ag NPs with 26-nm Au core and 9-nm Ag shell exhibit an excellent Raman enhancement effect.•PA can be directly detected ...in milk matrices without sample pretreatment.•The detection of trace PA in milk products using Au@Ag NPs as Raman amplifier is reported for the first time.•The label-free SERS technique can satisfy the practical requirements for screen PA in real samples.
A label-free surface-enhanced Raman scattering (SERS) strategy based on silver-coated gold nanoparticles (Au@Ag NPs) was developed for rapid detection of penicilloic acid (PA) in milk products. It has been demonstrated that core size and shell thickness of Au@Ag NPs are two critical variants affecting enhancement of Raman signals by coupling of two plasma resonance absorption. The Au@Ag NPs with 26-nm core and 9-nm Ag shell exhibit excellent Raman enhancement, in particular, upon the formation of hot spots through NPs aggregation induced by interaction between target molecules and Au@Ag NPs. Compared to the early studies limited to laboratory settings, our analytical approach is simple (without sample pretreatment), less time-consuming (within ∼3min) and inexpensive. The limit of detection of PA is 3.00ppm, 3.00ppm and 4.00ppm in liquid milk, yogurt and milk powder, respectively. The label-free SERS technique offers a potential for the on-site monitoring of chemical contaminants in milk products.
Cyclone Global Navigation Satellite System (CYGNSS) launched in recent years, provides a large amount of spaceborne GNSS Reflectometry data with all-weather, global coverage, high space-time ...resolution, and multiple signal sources, which provides new opportunities for the machine learning (ML) study of sea surface height (SSH) inversion. This article proposes for the first time two different CYGNSS SSH inversion models based on two widely used ML methods, back propagation (BP) neural network and convolutional neural network (CNN). The SSH calculated by using Danmarks Tekniske Universitet (DTU) 18 ocean wide mean SSH (MSSH) model (DTU18) with DTU global ocean tide model is used for verification. According to the strategy of independent analysis of data from different signal sources, the mean absolute error (MAE) of the BP and CNN models' inversion specular points' results during 7 days is 1.04 m and 0.63 m, respectively. The CLS 2015 product and Jason-3 data were also used for further validation. In addition, the generalization ability of the model, for 6 days and 13 days training sets, was also evaluated. For 6 days training set, the prediction results' MAE of the BP model is 11.59 m and 5.90 m for PRN2 and PRN4, and the MAE of the CNN model is 1.37 m and 0.97 m for PRN2 and PRN4, respectively. The results show that BP and CNN inversions are in high agreement with each product, and the CNN model has relatively higher accuracy and better generalization ability.
Despite the desirability of metal–organic frameworks (MOFs) as heterogeneous photocatalysts, current strategies available to enhance the performance of MOF photocatalysts are complicated and ...expensive. Herein, a simple strategy is presented for improving the activity of MOF photocatalysts by regulating the atomic interface structure of the metal active sites on the MOF. In this study, MOF (PCN‐222) is hybridized with cellulose acetate (CA@PCN‐222) through an optimized atomic interface strategy, which lowers the average valence state of Zr ions. The electronic metal‐support interaction mechanism of CA@PCN‐222 is revealed by evaluating the photocatalytic CO2 reduction reaction (CO2RR). The experimental results suggested that the electron migration efficiency at the atomic interface of the MOFs strongly coupled with cellulose is significantly improved. In particular, the CO2RR to formate activity of CA@PCN‐222 photocatalyst greatly increased from 778.2 to 2816.0 µmol g−1 compared with pristine PCN‐222 without cellulose acetate. The findings suggest that the strongly coupled metal–ligand moiety at the atomic interface of MOFs may play a synergistic role in heterogeneous catalysts.
MOF (PCN‐222) is hybridized with cellulose acetate (CA@PCN‐222) through an optimized atomic interface strategy, which lowers the average valence state of Zr ions. The CA@PCN222 exhibits high photocatalytic activity of CO2RR.
Owing to the unique coordination environment and high atom utilization efficiency, single atom catalysts have been considered as an ideal artificial enzyme to mimic natural enzymes. Herein, ...single-atom Fe nanozyme anchored on N-doped Ti
3
C
2
T
x
(Fe SA/N-Ti
3
C
2
T
x
) with asymmetrically coordinated Fe-N
1
C
2
configuration is synthesized by vacancy capture and heteroatom doping strategy, which exhibits excellent peroxidase-like activity. Based on the results of peroxidase catalytic kinetics and X-ray adsorption fine spectroscopy, the Fe-N
1
C
2
active sites in Fe SA/N-Ti
3
C
2
T
x
are responsible for the excellent performance. Furthermore, the developed Fe SA/N-Ti
3
C
2
T
x
can be employed to quantitative detection of melatonin (MT), which shows a wide linear detection range (0.01–100 µM) and an excellent detection limit (7.3 nM) in buffer, 0.01–100 µM and 7.8 nM in serum samples. Our work proves that MXene-based single atoms can be promising nanozyme in the field of bioassays.
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