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The phosphorus and zinc contained in zinc dialkyl dithiophosphate (ZDDP) caused severe environment pollution and catalyst poison. Thus, the phosphorus-free additive, such as borate esters, has become one of studying hot topics in the area of oil additive. However, the stability of hydrolysis greatly limited the use of borate esters. The purpose of this paper is to improve the stability of hydrolysis by synthesizing a new kind of N-containing heterocyclic borate ester (MTTDB) as a lubricant additive.

The tribological properties of novel borate ester (MTTDB) as an additive in the base oil were studied by a four-ball machine. The element composition and chemical state of the tribofilm were investigated by scanning electron microscopy, energy dispersive spectrometer and X-ray photoelectron spectroscopy.

The results showed that the base oil lubricated by MTTDB exhibited high hydrolytic stability, good anti-wear property and excellent extreme pressure performance. When 2.5 per cent MTTDB was added into the 100N base oil, the smallest wear scar diameter (0.46 mm) was obtained. Furthermore, the decomposed borate ester, organic sulfide adsorbed on the worn surface was detected, and S element reacted with the steel surface and generated FeSO4, both of which contributed to the formation of the tribofilm.

Based on N-containing heterocyclic compounds, for instance, thiadiazole derivatives, introducing nitrogen and sulfur elements into borate ester, a new kind of N-containing heterocyclic borate ester (MTTDB) exhibited excellent property in hydrolysis stability, friction-reducing, anti-wear and extreme pressure. This synthesized method would be helpful for the borate ester used as additive in engine oil, gear oil and other industrial lubricants.

For an entrant platform in the on-demand service market, choosing an appropriate employment model is critical. This study explores how the entrant optimally chooses the employment model to achieve better performance and investigates the optimal pricing strategies and wage schemes for both incumbent and entrant platforms.

Based on the Hotelling model, the authors develop a game-theoretic framework to study the incumbent's and entrant's optimal service prices and wage schemes. Moreover, the authors determine the entrant's optimal employment model by comparing the entrant's optimal profits under different market configurations and analytically analyze the impacts of some critical factors on the platforms' decision-making.

This study reveals that the impacts of the unit misfit cost of suppliers or consumers on the pricing strategies and wage schemes vary with different operational efficiencies of platforms. Only when both the service efficiency of contractors and the basic employee benefits are low, entrants should adopt the employee model. Moreover, a lower unit misfit cost of suppliers or consumers makes entrants more likely to choose the contractor model. However, the service efficiency of contractors has nonmonotonic effects on the entrant's decision.

This study focuses on an entrant's decision on the optimal employment model in an on-demand service market, considering the competition between entrants and incumbents on both the supplier and consumer sides, which has not been investigated in the prior literature.