Securing Parked Vehicle Assisted Fog Computing With Blockchain and Optimal Smart Contract Design

Vehicular fog computing(VFC)has been envisioned as an important application of fog computing in vehicular networks.Parked vehicles with embedded computation resources could be exploited as a supplement for VFC.They cooperate with fog servers to process offloading requests at the vehicular network edge,leading to a new paradigm called parked vehicle assisted fog computing(PVFC).However,each coin has two sides.There is a follow-up challenging issue in the distributed and trustless computing environment.The centralized computation offloading without tamper-proof audit causes security threats.It could not guard against false-reporting,free-riding behaviors,spoofing attacks and repudiation attacks.Thus,we leverage the blockchain technology to achieve decentralized PVFC.Request posting,workload undertaking,task evaluation and reward assignment are organized and validated automatically through smart contract executions.Network activities in computation offloading become transparent,verifiable and traceable to eliminate security risks.To this end,we introduce network entities and design interactive smart contract operations across them.The optimal smart contract design problem is formulated and solved within the Stackelberg game framework to minimize the total payments for users.Security analysis and extensive numerical results are provided to demonstrate that our scheme has high security and efficiency guarantee.

3D-printed mechanically strong and extreme environment adaptable boron nitride/cellulose nanofluidic macrofibers

Fibrous nanofluidic materials are ideal building blocks for implantable electrode,biomimetic actuator,wearable electronics due to their favorable features of intrinsic flexibility and unidirectional ion transport.However,the large-scale preparation of fibrous nanofluidic materials with desirable mechanical strength and good environment adaptability for practical use remains challenging.Herein,by fully taking advantage of the attractive mechanical,structural,chemical features of boron nitride(BN)nanosheet and nanofibrillated cellulose(NFC),a scalable and cost-effective three-dimensional(3D)printed macrofiber featuring abundant vertically aligned nanofluidic channels is demonstrated to exhibit a good combination of high tensile strength of 100 MPa,thermal stability of up to 230℃,ionic conductivity of 1.8×10^(−4)S/cm at low salt concentrations(<10^(−3)M).In addition,the versatile surface chemistry of cellulose allows us to stabilize the macrofiber at the molecular level via a facile postcross-linking method,which eventually enables the stable operation of the modified macrofiber in various extreme environments such as strong acidic,strong alkaline,high temperature.We believe this work implies a promising guideline for designing and manufacturing fibrous nanodevices towards extreme environment operations.

Pd nano-catalyst supported on biowaste-derived porous nanofibrous carbon microspheres for efficient catalysis

Environmental pollution caused by the presence of aromatic aldehydes and dyes in wastewater is a serious global concern. An effective strategy for the removal of these pollutants is their catalytic conversion, possibly to valuable compounds. Therefore, the design of efficient, stable and long-lifetime catalysts is a worthwhile research goal. Herein, we used nanofibrous carbon microspheres (NCM) derived from the carbohydrate chitin present in seafood waste, and characterized by interconnected nanofibrous networks and N/O-containing groups, as carriers for the manufacture of a highly dispersed, efficient and stable Pd nano-catalyst (mean diameter ca. 2.52 nm). Importantly, the carbonised chitin’s graphitized structure, defect presence and large surface area could promote the transport of electrons between NCM and Pd, thereby endowing NCM supported Pd catalyst with high catalytic activity. The NCM supported Pd catalyst was employed in the degradation of some representative dyes and the chemoselective hydrogenation of aromatic aldehydes;this species exhibited excellent catalytic activity and stability, as well as applicability to a broad range of aromatic aldehydes, suggesting its potential use in green industrial catalysis.

Selective C-C bonds formation,N-alkylation and benzo[d]imidazoles synthesis by a recyclable zinc composite

Earth abundant metals are much less expensive,promising,valuable metals and could be served as catalysts for the borrowing hydrogen reaction,dehydrogenation and heterocycles synthesis,instead of noble metals.The uniformly dispersed zinc composites were designed,synthesized and carefully characterized by means of XPS,EDS,TEM and XRD.The resulting zinc composite showed good catalytic activity for the N-alkylation of amines with amines,ketones with alcohols in water under base-free conditions,while unsaturated carbonyl compounds could also be synthesized by tuning the reaction conditions.Importantly,it was the first time to realize the synthesis of 2-aryl-1H-benzo[d]imidazole derivatives by using this zinc composite under green conditions.Meanwhile,this zinc catalyst could be easily recovered and reused for at least five times.

Microstructured capacitive sensor with broad detection range and long-term stability for human activity detection

In recent years,flexible stress sensors capable of monitoring diverse body movements and physiological signals have been attracting great attention in the fields of healthcare systems,human–machine interfaces,and wearable electronics.Inspired by the structure of natural eggshell inner membrane(ESIM),we developed a pressure sensor based on MXene(Ti_(3)C_(2)T_(x))/Ag NWs(silver nanowires)composite electrodes and the micro-structured dielectric layer to meet the application requirements of wide detection range and long-term stability for the sensors.In the light of the nanoscale-microarray of the dielectric layer and the rough surface of electrode materials,this pressure sensor is expected to allow great and persistent deformation during the loading process.As a result,the device is characterized by an improved sensitivity,fast response(in the millisecond range),wide detection range(0–600 kPa),and long-term stability.The outstanding performance of the proposed sensor makes it possible to detect various human activities,such as speaking,air blowing,clenching,walking,finger/knee/elbow bending,and striking,demonstrating its good application prospects in wearable and flexible electronic devices.

Raman imaging-assisted customizable assembly of MOFs on cellulose aerogel

Because of a weak interface-bonding force between metal–organic frameworks(MOFs)and substrates and the loss of customization in structural designs owing to the lack of the regulation of ion sites,MOFs tend to escape from the constructed composite template.In this study,the as-prepared 2,2,6,6-tetramethylpiperidyl-1-oxyl(TEMPO)-oxidized algae cellulose nanofibers(TACFs)were used to chelate metal ions at controllable sites and subsequently firmly entangle the assembled MOF crystals.The distribution of ions and synthesized MOFs inside the gel was monitored using Raman imaging technology,which provided an intuitive approach for visually observing the ions and MOF distribution.Using this technology,the synthesized customizable TACFs@ZIF-67 aerogels exhibited a high specific surface area(734.7 m^(2)/g),low density(6.18 mg/cm^(3)),controlled particle distribution,good underwater structural stability,and excellent adsorption of dyes.This study provides a way for solving the dispersion problem of MOFs in nanofibrous aerogels using Raman imaging technology–assisted microcosmic fixed-point design.

Quaternized chitosan-assisted in situ synthesized CuS/cellulose nanofibers conductive paper for flexible electrode

Cellulose nanofibers(CNF)are considered to be a potential substrate of energy material for energy storage devices due to the foldable,lightweight,recyclable and environmentally friendly feature.However,the energy materials tend to distribute unevenly or fall off from CNF easily,resulting in the decrease of the devices’overall performance.Here,for the first time,we used quaternized chitosan(QCS)as stabilizer and adhesive to in situ synthesize and deposite copper sulfide nanocrystals(CuS-NCs)on CNF and further obtained the conductive paper for flexible supercapacitors.In the presence of QCS,CuS-NCs deposited in situ on CNF can be capped and stabilized by the QCS molecular chains for uniform distribution,which is conducive to the capacitive behavior and electrochemical stability of composite paper.The result shows that the specific capacitance of the composite paper was as high as 314.3 F/g at a current density of 1 A/g,a high rate capacitance of 252.6 F/g was achieved even at a high current density of 10 A/g.It reveals that the composite paper exhibited better electrochemical performance than many other CuS-based electrode materials for supercapacitor.More importantly,the composite paper performed well in various folding state without changing much electrochemical performance.Therefore,this work provides a novel strategy to in situ fabricate paper-based electrode for nextgeneration flexible energy-storage system.