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Mineral particles are ubiquitous in the atmosphere and exhibit an important effect on the photooxidation of volatile organic compounds (VOCs). However, the role of mineral particles in the photochemical oxidation mechanism of VOCs remains unclear. Hence, the photooxidation reactions of acrolein (ARL) with OH radical (OH) in the presence and absence of SiO2 were investigated by theoretical approach. The gas-phase reaction without SiO2 has two distinct pathways (H-abstraction and OH-addition pathways), and carbonyl-H-abstraction is the dominant pathway. In the presence of SiO2, the reaction mechanism is changed, i.e., the dominant pathway from carbonyl-H-abstraction to OH-addition to carbonyl C-atom. The energy barrier of OH-addition to carbonyl C-atom deceases 21.33 kcal/mol when SiO2 is added. Carbonyl H-atom of ARL is occupied by SiO2 via hydrogen bond, and carbonyl C-atom is activated by SiO2. Hence, the main product changes from H-abstraction product to OH-adduct in the presence of SiO2. The OH-adduct exhibits a thermodynamic feasibility to yield HO2 radical and carboxylic acid via the subsequent reactions with O2, with implications for O3 formation and surface acidity of mineral particles.

Organosulfate (OSA) nanoparticles, as secondary organic aerosol (SOA) compositions, are ubiquitous in urban and rural environments. Hence, we systemically investigated the mechanisms and kinetics of aqueous-phase reactions of 1-butanol/1-decanol (BOL/DOL) and their roles in the formation of OSA nanoparticles by using quantum chemical and kinetic calculations. The mechanism results show that the aqueous-phase reactions of BOL/DOL start from initial protonation at alcoholic OH-groups to form carbenium ions (CBs), which engage in the subsequent esterification or oligomerization reactions to form OSAs/organosulfites (OSIs) or dimers. The kinetic results reveal that dehydration to form CBs for BOL and DOL reaction systems is the rate-limiting step. Subsequently, about 18% of CBs occur via oligomerization to dimers, which are difficult to further oligomerize because all reactive sites are occupied. The rate constant of BOL reaction system is one order of magnitude larger than that of DOL reaction system, implying that relative short-chain alcohols are more prone to contribute OSAs/OSIs than long-chain alcohols. Our results reveal that typical long-chain alcohols contribute SOA formation via esterification rather than oligomerization because OSA/OSI produced by esterification engages in nanoparticle growth through enhancing hygroscopicity.

In this work, an Au modified Bi2O3-TiO2 (Au/Bi2O3-TiO2) hybrid is developed as a simple and effective photocatalyst for the production of H2O2. The modification of Bi2O3 improves the charge separation of photocatalyst and significantly enhances the photocatalytic activity of Au/TiO2 for H2O2 production. In-situ electron spin resonance studies shows stepwise single-electron oxygen reduction reaction (ORR) on the Au/Bi2O3-TiO2 photocatalyst for the production of H2O2. This work demonstrates the importance of heterojunction structure photocatalyst for improved performance of TiO2 in order to produce concentrated H2O2.

This research proposes an improved particle filter tracking algorithm based on SGA (the adaptive genetic algorithm supervised by population convergence). In order to improve the robustness and efficiency of the particle filter tracker in various tracking scenarios, this study proposes an adaptive feature selection strategy based on Harris corner detection, SIFT features and colour features. In addition, the tracking frame scale of the traditional target tracking algorithm is fixed in the tracking process, which leads to many problems such as more invalid features and lower positioning accuracy. To solve these problems, this study proposes an adaptive tracking frame scale adjustment model based on the spatial position of particles. Furthermore, considering that the scale adaptive model cannot accurately reflect the target rotation deformation, this paper proposes an adaptive tracking frame scale and direction adjustment model based on the covariance descriptors to accurately track the rotation of the target and further reduce the invalid features of the rectangle frame. The extensive empirical evaluations on the benchmark dataset (OTB2015) and VOT2016 dataset demonstrate that the proposed method is very promising for the various challenging scenarios.

A wideband multilayered inverted truncated conical dielectric resonator antenna (ITCDRA) based on 3D-printing technology is proposed. It comprises three truncated conical dielectric rings with decreasing effective dielectric constants from inside to outside. To facilitate the 3D-printing, hollow cube unit cells are utilized to reconstruct this multilayered DR. A coaxial SMA probe is used to excite this DRA with multiple TM modes. By merging these modes, a measured -10-dB impedance bandwidth of 60.8% (4.43-8.3 GHz) can be obtained. Besides, the DR is mounted on a serrated ground to obtain stable realized gain with the measured 1-dB gain-fluctuation bandwidth of 55.3% (4.55-8.03 GHz).

A wideband multilayered cylindrical dielectric resonator antenna (CDRA) using 3D-printing technology is investigated. It includes three cylindrical dielectric rings with decreasing effective dielectric constants, interspersed with two air layers. This multilayered DRA is combined on a cylindrical insert layer with a low dielectric constant to get better impedance matching. To facilitate the 3D-printing, a simple hollow cube unit cell is utilized to reconstruct this multilayered DR. A coaxial probe is used to excite this DRA with multiple TM modes. By merging these modes, a wide measured -10 dB impedance bandwidth of 65.7% (3.56–7.04 GHz) can be obtained, with measured realized gain varying within 2.3 dB across the passband.

To assess the ozone depletion potentials of hydrochlorofluoromethanes (HCFMs) and hydrochlorofluoroethanes (HCFEs), atmospheric behaviors of these chlorofluorocarbon alternatives with OH radicals were investigated using quantum chemical and kinetic calculations. The results showed that the H-abstraction reactivity of HCFMs initiated by OH radicals enhances with the increase of the chlorination degree. The intermediate alkyl radicals can generate stable chlorofluorocarbons (CFCs) through self-reactions, which may compete with the reactions of radicals with O2 molecules and increase the risk of ozone layer depletion. The self-reactions of HCFEs result in the increase of carbon chain length, and formed hydrochlorofluorocarbons can further react with OH radicals.

In this paper, we investigated the frictional behaviors of the mixed self-assembled molecular films of the fluoroalkylsilane (FAS) molecules and non-fluoroalkylsilane (n-FAS) molecules with different chain length covalently absorbed on silicon surfaces, characterized by the universal ball-disk UMT-2 experimental tester under aqueous solution conditions. The surfaces of the substrate modified by mixed self-assembled molecular films were examined by X-ray photoelectron spectroscopy (XPS) and contact angle measurements. The formation processes of the molecular films were characterized by quartz crystal microbalance (QCM). The results indicated that it would take a longer time to reach the adsorption equilibrium of the molecular films with the increment of carbon chain length. The measured tribological results showed that the mixing of the fluoroalkylsilane and non-fluoroalkylsilane enhance the lubrication and decrease the friction and wear compared to the one-component thin films. This may be caused by the reduced excitation of the energy dissipation channels.

The poly (N-isopropylacrylamide) brush was covalently bonded on an initiator-coated silicon wafer via surface-initiated atom transfer radical polymerization. The polymer brush was (76.2±0.1) nm in thickness (by ellipsometer) with a grafting density of ca. 0.27 chains/nm2. The tribological properties of the poly (N-isopropylacrylamide) brush were investigated by means of ball-on-disk tests in a rotational mode under water lubrication for tribological application. The experimental results exhibited a low friction coefficient of ca. 0.03. The excellent lubrication property of the brush was due to its amide groups in the polymer chains. It was supposed that the good lubrication property of the brush was attributed to the cross-linked polymer network formed by the hydrogen bond association of N—H…O==C and the water molecular layer adsorbed by the terminal amide groups in the brush. The poly (N-isopropylacrylamide) solution also exhibits a lubrication property due to physical adsorption of the polymer chains.

An overview of the advances in studies on tribology of molecular deposition (MD) films is presented here to summarize the studies of nanofrictional properties, adhesion, wear and mechanical behavior, as well as the molecular dynamics simulation of nanotribological properties of the film in the last decade. Some key research topics which need to be investigate further are addressed.

Inorganic-organic hybrid nanoparticles molecular deposition films were fabricated by extending the method of nucleation and growth of particles in polymer assemblies. Poly (diallyldimethylammonium chloride) (PDDA) and poly (styrenesulfonate) sodium salt (PSS) were applied as polycation and polyanion respectively. At first, PDDA/PSS films were obtained by alternately depositing PDDA and PSS on the cleaned substrate with molecular deposition (MD) method. Then, follow’s alternately dipped the precursor polyelectrolyte multilayer MD films into AgNO3 and H4SiW12O40 aqueous solutions. Repeating the above synthesis process, Ag4SiW12O40 nanoparticles were synthesized in the polyelectrolyte multilayer films in-situ. UV-vis absorption spectra indicate that the Ag4SiW12O40 nanoparticles grew gradually in the synthesis process. The structure and nanotribological properties of hybrid nanoparticles multilayer films were analyzed by atomic force microscope (AFM) and the antiwear life was analyzed by micro-friction and wear test machine. It was found that these films had small friction force and high antiwear life. The MD film had best tribological properties when the cycle number is six. Nanoparticles within the MD films can enhance antiwear life of MD films attributed to nanoparticles possess load-carrying capacity, and decrease the mobility of the polymer chain segments which can undergo reversible shear deformation.

In this paper, we report the tribological properties of self-assembled molecular (SAM) films of fluoroalkylsilanes and non-fluoroalkylsilanes, with different chain-lengths, adsorbed on Si substrate surfaces by covalent bonds. The SAM films were characterized using a universal ball-disk experimental tester in aqueous solutions. The substrate surface was examined by X-ray photoelectron spectroscopy (XPS), and the SAM films adsorbed on the Si surfaces were inspected by contact angle measurements and XPS. Lubrication studies revealed that several kinds of fluoroalkylsilanes had similar friction coefficients; the small differences were attributed to the chain flexibility. In contrast, differences in the aqueous lubrication properties of SAM films of non-fluoroalkylsilanes were clearly identified. It is suggested that substitution with fluorine atoms and the surface affinities of fluoroalkylsilanes contributed to redistribution of surface changes, causing variations in lubrication behaviors.