Contract-Optimization Approach (COA): A New Approach for Optimizing Service Caching, Computation Offloading, and Resource Allocation in Mobile Edge Computing Network.

An optimal method for resource allocation based on contract theory is proposed to improve energy utilization. In heterogeneous networks (HetNets), distributed heterogeneous network architectures are designed to balance different computing capacities, and MEC server gains are designed based on the amount of allocated computing tasks. An optimal function based on contract theory is developed to optimize the revenue gain of MEC servers while considering constraints such as service caching, computation offloading, and the number of resources allocated. As the objective function is a complex problem, it is solved utilizing equivalent transformations and variations of the reduced constraints. A greedy algorithm is applied to solve the optimal function. A comparative experiment on resource allocation is conducted, and energy utilization parameters are calculated to compare the effectiveness of the proposed algorithm and the main algorithm. The results show that the proposed incentive mechanism has a significant advantage in improving the utility of the MEC server.

Enhancing Data Freshness in Air-Ground Collaborative Heterogeneous Networks through Contract Theory and Generative Diffusion-Based Mobile Edge Computing.

Mobile edge computing is critical for improving the user experience of latency-sensitive and freshness-based applications. This paper provides insights into the potential of non-orthogonal multiple access (NOMA) convergence with heterogeneous air-ground collaborative networks to improve system throughput and spectral efficiency. Coordinated resource allocation between UAVs and MEC servers, especially in the NOMA framework, is addressed as a key challenge. Under the unrealistic assumption that edge nodes contribute resources indiscriminately, we introduce a two-stage incentive mechanism. The model is based on contract theory and aims at optimizing the utility of the service provider (SP) under the constraints of individual rationality (IR) and incentive compatibility (IC) of the mobile user. The block coordinate descent method is used to refine the contract design and complemented by a generative diffusion model to improve the efficiency of searching for contracts. During the deployment process, the study emphasizes the positioning of UAVs to maximize SP effectiveness. An improved differential evolutionary algorithm is introduced to optimize the positioning of UAVs. Extensive evaluation shows our approach has excellent effectiveness and robustness in deterministic and unpredictable scenarios.

CoFe Alloy-Coupled Mo2C Wrapped by Nitrogen-Doped Carbon as Highly Active Electrocatalysts for Oxygen Reduction/Evolution Reactions.

Molybdenum carbide (Mo2C) with a Pt-like d-band electron structure exhibits certain activities for oxygen reduction and evolution reactions (ORR/OER) in alkaline solutions, but it is questioned due to its poor OER stability. Combining Mo2C with transition metals alloy is a feasible way to stabilize its electrochemical activity. Herein, CoFe-Prussian blue analogues are used as a precursor to compound with graphitic carbon nitride and Mo6+ to synthesize FeCo alloy and Mo2C co-encapsulated N-doped carbon (NG-CoFe/Mo2C). The morphology of NG-CoFe/Mo2C (800 °C) shows that CoFe/Mo2C heterojunctions are well wrapped by N-doped graphitic carbon. Carbon coating not only inhibits growth and agglomeration of Mo2C/CoFe, but also enhances corrosion resistance of NG-CoFe/Mo2C. NG-CoFe/Mo2C (800 °C) exhibits an excellent half-wave potential (E1/2 = 0.880 V) for ORR. It also obtains a lower OER overpotential (325 mV) than RuO2 due to the formation of active species (CoOOH/ß-FeOOH, as indicated by in-situ X-ray diffraction tests). E1/2 shifts only 6 mV after 5000 ORR cycles, while overpotential for OER increases only 19 mV after 1000 cycles. ORR/OER performances of NG-CoFe/Mo2C (800 °C) are close to or better than those of many recently reported catalysts. It provides an interfacial engineering strategy to enhance the intrinsic activity and stability of carbides modified by transition-metals alloy for oxygen electrocatalysis.

catena-Poly[(dichloridozinc)-µ-4,4'-bis-[(1H-imidazol-1-yl)meth-yl]biphenyl-κ(2)N(3):N(3')].

In the title compound, [ZnCl(2)(C(20)H(18)N(4))](n), the Zn(II) ion lies on a twofold rotation axis and is four-coordinated in a tetra-hedral geometry defined by two Cl anions and two N atoms from two 4,4'-bis-[(imidazol-1-yl)meth-yl]biphenyl ligands. The mid-point of the ligand is located on an inversion center, and shows a trans conformation. The ligands link the Zn(II) ions, forming a chain structure along [10-1].

catena-Poly[(dichloridozinc)-µ-1-{4-[(1H-imidazol-1-yl)meth-yl]benz-yl}-1H-imidazole-κ(2)N(3):N(3')].

The asymmetric unit of the title compound, [ZnCl(2)(C(14)H(14)N(4))](n), contains a Zn(II) ion situated on a twofold rotation axis and one-half of a 1-{4-[(1H-imidazol-1-yl)meth-yl]benz-yl}-1H-imidazole (L) ligand with the benzene ring situated on an inversion center. The Zn(II) ion is coordinated by two chloride anions and two N atoms from two L ligands in a distorted tetra-hedral geometry. The L ligands bridge ZnCl(2) fragments into polymeric chains parallel to [20-1].

Novel polyimides containing flexible carbazole blocks with electrochromic and electrofluorescencechromic properties.

A series of polyimides (PIs) were prepared by polycondensation of a diamine monomer with five anhydrides (1,2,4,5-benzenetetracarboxylic anhydride (BTA), 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTD), 3,3',4,4'-biphenyltetracarboxylic dianhydride (BTD), 4-[(1,3-dihydro-1,3-dioxo-5-isobenzofuranyl)oxy]-1,3-isobenzofurandione (DDII), and 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BPTD)), which have anodic electrochromic (EC) properties. These PIs not only show good solubility and thermal stability, but also demonstrate stable electrochemical oxidation behavior and good EC properties, and the highest retained electroactivity reaches 99% after 600 cycles. In addition, the series of PIs exhibit excellent electrofluorescencechromic (EFC) properties. Therefore, the novel materials will contribute to the application of EC or EFC displays in the future.

Mussel-inspired antifouling magnetic activated carbon for uranium recovery from simulated seawater.

Undesirable bio-adhesion of microalgae on adsorbent can influence its adsorption capacity. In this report, we fabricated a novel mussel-inspired antifouling magnetic activated carbons which derived orange peel by integrated biosorption-pyrolysis process (MACs@PDA-Ag), via co-functionalization of poly-dopamine (PDA) and Ag nanoparticles (AgNPs), for the recovery of uranium (VI) from simulated seawater with antimicrobial adhesion performance; this process did not require an additional reducing agent. The effect of pH, concentration, contact time, fouling test against nitzschia closterium f.minutissima (GY-H8) were studied. Compared with MACs (632.91 mg/g at pH 7.0), the calculated maximum adsorption capacity of MACs@PDA-Ag increased to 657.89 mg/g at pH 8.0 and showed good recyclability. These data all fitted well with the Langmuir and pseudo-second order models. The possible removal mechanism by XPS is chelation (catechol hydroxyls, amine/imine units, the metal-oxygen and carboxylic) with uranium (VI). The antifouling tests indicated that the AgNPs-modified materials displayed the antimicrobial adhesion behavior, and the viability of the microorganism was not impacted. Thereby, the direct deposition of AgNPs onto the adsorbent has shown great potential for uranium (VI) recovery with an antifouling benefit and is environmentally friendly.

Biocompatible core-shell electrospun nanofibers as potential application for chemotherapy against ovary cancer.

Polyvinyl alcohol/chitosan (PVA/CS) core-shell nanofibers are successfully fabricated by a simple coaxial electrospinning method, in which PVA forms the core layer and CS forms the shell layer. With the change of the feed ratio between PVA and CS, the surface morphology and the microstructures of the nanofibers are largely changed. The as-prepared core-shell fibers can be used as a carrier for doxorubicin (DOX) delivery. FT-IR analysis demonstrates that hydrogen bond between CS and PVA chains forms. The results of in vitro cytotoxicity test indicate that the core-shell fibers are completely biocompatible and the free DOX shows higher cytotoxicity than the DOX loaded nanofibers. The standing PVA/CS core-shell fibers remarkably promote the attachment, proliferation and spreading of human ovary cancer cells (SKOV3). Via observing by confocal laser scanning microscopy (CLSM), the DOX released from the fibers can be delivered into SKOV3 cell nucleus, which is significant for the future tumor therapy. And, the as-prepared fibers exhibit controlled release for loaded DOX via adjusting the feed ratio between PVA and CS, and the DOX loaded nanofibers are quite effective in prohibiting the SKOV3 ovary cells attachment and proliferation, which are potential for chemotherapy of ovary cancer.

Electrospun polyvinyl alcohol/chitosan composite nanofibers involving Au nanoparticles and their in vitro release properties.

Au nanoparticles (Au NPs) containing polyvinyl alcohol (PVA)/chitosan (CS) composite nanofibers were successfully prepared by a simple and effective method called electrospinning. Au NPs were firstly synthesized under a mild condition with CS as the reducing agent and stabilizer, followed by being mixed with PVA solution and then the resulting fibers were fabricated. The research indicated that Au NPs were indeed doped into the as-prepared fibers and the composite fibers well preserved Au NPs' unique optical characteristics. Additionally, with the adjustment of the weight ratios between PVA and CS, the diameter distribution and the morphology of the nanofibers were largely changed. In vitro drug release experiments demonstrated that the drug release rate can be conveniently controlled by changing the crosslink time.