[en] Highlights: • We defined 7 effects of excess air and quantitative indicators on NOx emissions. • Contributions of N_2, O_2 and Ar on the thermal effect are separately 85%, 14% and 1%. • Contributions of N_2 and Ar on the dilution effect are 98.8% and 1.2%, respectively. • The high level of N_2 in air is the main reason why NOx emissions decrease with λ. - Abstract: This paper presents the effects of N_2, O_2 and Ar in excess air on combustion and NOx emissions of a natural gas spark-ignition engine. Based on Arrhenius Law and Zeldovich Mechanism, seven different kinds of effects were defined as well as their quantitative indicators. Excess air and N_2 were separately added into the intake charge with fuel remaining unchanged in a 6-cylinder turbocharged natural gas engine. The results show that the essential reason why NOx emissions vary with increasing excess air ratio (λ) is that the oxidation effect of O_2 varies with the in-cylinder temperature, which is controlled by the thermal effect of excess air. The contributions of N_2, O_2 and Ar on the thermal effect are 82.6–86.1%, 13.3–16.7% and 0.6–0.7%, respectively. The chemical effect of O_2 is fully offset by the dilution effect of N_2 and Ar. The contributions of N_2 and Ar on the dilution effect are 98.31% and 1.69%, respectively. The increase of NOx emissions caused by O_2 is found to be increased first and then decreased with increasing λ. From the view of the composition of air, the high level of N_2 is the main reason why NOx emissions decrease significantly with increasing λ

[en] This paper calculates the equilibrium structure and the potential energy functions of the ground state (X²Σ⁺) and the low lying excited electronic state (A²II) of CN radical are calculated by using CASSCF method. The potential energy curves are obtained by a least square fitting to the modified Murrell–Sorbie function. On the basis of physical theory of potential energy function, harmonic frequency (ω_e) and other spectroscopic constants (ω_eχ_e, β_e and α_e) are calculated by employing the Rydberg–Klein–Rees method. The theoretical calculation results are in excellent agreement with the experimental and other complicated theoretical calculation data. In addition, the eigenvalues of vibrational levels have been calculated by solving the radial one-dimensional Schrödinger equation of nuclear motion using the algebraic method based on the analytical potential energy function. (atomic and molecular physics)

[en] In this paper, a crosslinked carboxymethyl starch (CCMS) was prepared with corn starch as the raw material, epichlorohydrin as the crosslinking agent, and chloroacetic acid as the etherifying agent through a series of crosslinking, alkalization, and etherification reactions, respectively. Nano-TiO₂ was loaded onto the surface of the CCMS by the sol-gel method to obtain a TiO₂/CCMS composite. The TiO₂/CCMS composite was characterized by XPS, XRD, SEM, and BET. XPS showed that the surface chemical composition of the TiO₂/CCMS composite material contained titanium; XRD diffraction patterns indicated that the crystal form of the TiO₂/CCMS composite was a combination of the CCMS and anatase TiO₂. The surface morphology obtained by SEM showed that there were nano-TiO₂ particles on the surface of the CCMS. The specific surface area of the TiO₂/CCMS composite was larger than that of CCMS. The adsorption-photodegradation performance of the TiO₂/CCMS composite was also studied under UV irradiation, and the results showed that significant adsorption-photodegradation synergies occurred.