Insight into Hydrolytic Stability and Tribological Properties of B-N Coordination Tung Oil-Based Lubricant Additive in Water

A tung oil-based boron-nitrogen coordination polymer(TWE-BN)was specially designed and synthesized as a highly efficient water-based lubricant additive,which has been beneficial to both energy conservation and conducive to environmental protection.Its hydrolysis stability and tribological properties in water were investigated.To better research the lubricating properties,and thus to understand the interaction between the surface and the lubricating additives.Herein,both experimental and theoretical computations based on density functional theory(DFT)were performed.The addition of TWE-BN reduces the water friction coefficient and wear scar diameter,and the maximum non-seizure load increased from 93 to 726 N.Moreover,the anti-corrosion ability on copper was classified as 1b level.The stainless-steel surface was analyzed using scanning electron microscopy(SEM)and X-ray photoelectron spectroscopy(XPS).In hydrolytic stability testing,TWE-BN was better than nitrogen-free tung oil-based lubricant additive(TWE-B)and remained non-hydrolyzed for at least 15 days,implying the feasibility of tung oil-based boron-nitrogen coordination as highly effective and hydrolytic stability lubricant additives.

Preparation and Properties of Vegetable-Oil-Based Thioether Polyol and Ethyl Cellulose Supramolecular Composite Films

Ethyl cellulose(EC),an important biomass-based material,has excellent film-forming properties.Nevertheless,the high interchain hydrogen bond interaction leads to a high glass transition temperature of EC,which makes it too brittle to be used widely.The hydroxyl group on EC can form a supramolecular system in the form of a non-covalent bond with an effective plasticizer.In this study,an important vegetable-oil-based derivative named dimer fatty acid was used to prepare a novel special plasticizer for EC.Dimer-fatty-acid-based thioether polyol(DATP)was synthesized and used to modify ethyl cellulose films.The supramolecular composite films of DATP and ethyl cellulose were designed using the newly-formed van der Waals force.The thermal stability,morphology,hydrophilicity,and mechanical properties of the composite films were all tested.Pure EC is fragile,and the addition of DATP makes the ethyl cellulose films more flexible.The elongation at the break of EC supramolecular films increased and the tensile strength decreased with the increasing DATP content.The elongation at the break of EC/DATP(60/40)and EC/DATP(50/50)was up to 40.3%and 43.4%,respectively.Noticeably,the thermal initial degradation temperature of the film with 10%DATP is higher than that of pure EC,which may be attributed to the formation of a better supramolecular system in this composite film.The application of bio-based material(EC)is environmentally friendly,and the novel DATP can be used as a special and effective plasticizer to prepare flexible EC films,making it more widely used in energy,chemical industry,materials,agriculture,medicine,and other fields.

Multifunctional Lubricant Additive Improves Lubrication and Antioxidation Properties of Tung Oil

It is of considerable significance to develop efficient and environmentally friendly machinery lubricant additives because of the increasing depletion of petrochemical resources and severe environmental problems.Herein,we proposed a facile strategy to synthesize a multifunctional vegetable oil-based lubricant via the lignin derivative vanillin coupled to amine and diethyl phosphite to produce a lubricating additive with both extreme pressure and antioxidant properties.Compared with pure tung oil,the lubricating and antioxidant performance of tung oil is significantly improved after adding additives.Adding the 1.0 wt%additive to the tung oil reduced the friction wear coefficient and the volume,and the oxidation induction time was much longer than pure tung oil.

Ambient Backscatter Communications over NOMA Downlink Channels

In this paper,we investigate the performance of commensal ambient backscatter communications(AmBC)that ride on a non-ortho go nal multiple access(NOMA)downlink transmission,in which a backscatter device(BD)splits part of its received signals from the base station(BS)for energy harvesting,and backscatters the remaining received signals to transmit information to a cellular user.Specifically,under the power consumption constraint at BD and the peak transmit power constraint at BS,we derive the optimal reflection coefficient at BD,the optimal total transmit power at BS,and the optimal power allocation at BS for each transmission block to maximize the ergodic capacity of the ambient backscatter transmission on the premise of preserving the outage performance of the NOMA downlink transmission.Furthermore,we consider a scenario where the BS is restricted by a maximum allowed average transmit power and the reflection coefficient at BD is fixed due to BD’s low-complexity nature.An algorithm is developed to determine the optimal total transmit power and power allocation at BS for this scenario.Also,a low-complexity algorithm is proposed for this scenario to reduce the computational complexity and the signaling overheads.Finally,the performance of the derived solutions are studied and compared via numerical simulations.

Tribological Behavior of Plant Oil-Based Extreme Pressure Lubricant Additive in Water-Ethylene Glycol Liquid

A water-soluble lubricant additive(RSOPE)was prepared by esterification reaction using fatty acid from rubber seed oil.The RSOPE was added into water-ethylene glycol(W-EG)solution as lubricant additive.Dispersion stability and rheological properties were investigated.We used a four-ball tribotester to assess the lubrication performance of W-EG based fluid with the RSOPE additive.The stainless-steel surface was analyzed using scanning electron microscopy(SEM)and X-ray photoelectron spectroscopy(XPS).Good dispersion stability was observed in the RSOPE/W-EG solutions.Furthermore,non-Newtonian fluid behavior at low shear rates and Newtonian fluid behavior at high shear rates was exhibited.The addition of RSOPE into water-glycol reduced the friction coefficients(COF)and wear scar diameters(WSD).The maximum non-seizure loads(PB)increased from 98 N to 752 N and the W-EG solution with RSOPE had good corrosion resistance properties.Good tribological performances for W-EG solution with RSOPE were attributed to the boundary tribofilm composed of iron oxide,iron phosphide and so on.

Thermally Reversible,Self-Healing Polyurethane Based on Propyl Gallate and Polyurethane Prepolymers with Varied Isocyanate Content

Thermosetting polyurethanes are widely used in various fields owing to their excellent elasticity,strength and solvent resistance.Three environmental friendly propyl gallate-based self-healing polyurethanes were prepared from polyurethane prepolymers with varying isocyanate content.The thermal stabilities of the polyurethanes were tested using thermogravimetric analysis.Their self-healing and mechanical properties were analyzed using a universal testing machine and dynamic thermomechanical analysis.The polyurethanes were found with high self-healing ability and excellent mechanical properties due to the absence of phenolic carbamate.These qualities improved with increased isocyanate content and the prolonged selfhealing time.We found,therefore,that the propyl gallate-based polyurethane has potential for use in industrial applications as self-healing materials.

Modeling and coverage analysis of heterogeneous sub-6GHz-millimeter wave networks

The joint adoption of sub-6GHz and millimeter wave(mmWave)technology can prevent the blind spots of coverage,enabling comprehensive coverage while realizing high-speed communication rate.According to the sensitivity of mmWave,base stations should be more densely deployed,which is not well described by existing Poisson hole process(PHP)and the Poisson point process(PPP)models.This paper establishes a sub-6GHz and mmWave hybrid heterogeneous cellular network based on the modified Poisson hole process(MPHP).In our proposed model,the sub-6GHz base stations follow the PPP,and the mmWave base stations(MBSs)follow MPHP distribution.The expressions of the coverage probability are derived by using the interference calculation method of integrating the nearest sector exclusion area.Our theoretical analysis has been verified through simulation results,suggesting that the increase in the cell radius decreases the coverage probability of signal-to-interference-plus-noise ratio(SINR),whereas the increase in the sector parameter has the opposite effect.The variation of sub-6GHz base stations(SBSs)density imposes more significant impact than the MBSs on the SINR coverage probability.In addition,the decrease in MBSs density will reduce the average bandwidth allocated to the user equipment(UE),thus reducing the rate coverage probability.

Effect of different combinations of emulsifier and wall materials on physical properties of spray-dried microencapsulated swida wilsoniana oil

Spray drying was used to produce microencapsulated Wilson’s dogwood(Swida wilsoniana)oil.The influences of the emulsifier and wall materials on the encapsulation were studied in order to produce high quality encapsulated S.wilsoniana oil.The emulsions were prepared by using lecithin(L)and Tween 80(T)with different hydrophilic-lipophilic balance.Results indicated that the stable emulsion was obtained using T and L as the compound emulsifier at a ratio of 4/6(w/w).By virtue of the compound emulsifier(T/L 4/6),the microencapsulation efficiency(MEE)reached 91%,and the oil loading up to 35%was achieved.We also examined the influence of the wall materials on the microencapsulation of S.wilsoniana oil.All the three wall materials exhibited high MEE(>85%),and the highest MEE(95.20%)was obtained with sodium caseinate/lactose.All the S.wilsoniana oil encapsulated with the three wall materials exhibited nearly spherical microcapsules without pores or cracks,thus protecting the oil from oxygen.

Analysis and comparison of tribological performance of fatty acid-based lubricant additives with phosphorus and sulfur

Two environmentally friendly,water-based lubricant additives(phosphorus-containing ricinoleic acid(PRA)and sulfur-containing ricinoleic acid(SRA))were prepared.The lubrication perfor-mance of the additives in a water-based lubricant was tested using a four-ball tribotester.The stainless steel surface was analyzed by using scanning electron microscopy(SEM)and X-ray pho-toelectron spectroscopy(XPS).The additives reduced the coefficient of friction(COF)value,wear scar diameter(WSD)and improved the extreme pressure(PB)value.Water-based fluids con-taining the PRA exhibited lower COF,WSD,and PB values than the SRA.The good tribological performances of the PRA and SRA were attributed to the synergistic action of long aliphatic chains and highly active phosphorus and sulfur elements.

Research and design of CRT-based homomorphic ciphertext database system

The cloud’s storage and query of private information have the cryptographic scholar due to the proliferation of cloud computing.In the traditional query mode,the private information stored in the cloud is at risk of being leaked.In order to solve this problem,a cloud ciphertext database system based on homomorphic encryption is a valid workaround.This paper presents a new cloud ciphertext database system model,which is based on the existing ciphertext database mode research and homomorphic properties.This paper also implements a ciphertext database system based on a CRT-based additive homomorphic scheme according to the model.Through theoretical analysis,the model is CPA-level safe and correct.The experimental results show that users can correctly query and download the data in the ciphertext database on the untrusted cloud server through the model,and it has efficiency advantages.