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We selected 6 species of landscape plants growing under different pollution levels and performed quantitative determination of PM2.5 adsorption. We compared the measured adsorption to the leaf morphology and the water-soluble ion content. The results indicated that the pollution level and plant leaf surface PM2.5 adsorption capacity were positively correlated. There was variation in the leaf area PM2.5 adsorption capacity for plants in different locations, allowing us to determine species-specific effects and effects of different pollution levels. The results of the study have important significance to design strategies to reduce urban air particulate matter pollution and improve air quality.

The composite overwrapped pressure vessel (COPV) with its excellent properties is used for high-pressure storage in aerospace industries. Before they can be reliably incorporated into space flight applications, a significant amount of work has been conducted for better predicting the condition status and residual life of COPVs. A novel MXene film sensor technology that can provide real-time and in situ structural health monitoring of composite structures was proposed in this work. An excellent MXene film sensor can be obtained based on the method proposed in this paper. Before sensor is applied to pressure vessels, coupon tests include tensile loading testing and fatigue loading testing is carried out. For coupon tests, the piezoresistive response of MXene sensor is understood. MXene sensors made on a flexible printed circuit (FPC) have been integrated into a composite pressure vessel, and are used to monitor changes in the hoop and axial strain fields during hydraulic pressure tests. The piezoresistive response of MXene sensor is obtained and the main working mechanism of MXene is explained. The distributed strain measurement of the vessel provides a more efficient process of monitoring structural integrity to further understand the failure mechanisms of the vessel.

Changes in the surface wettability of poly(p-phenylene benzobisoxazole) (PBO) fibers were investigated by thermogravimetric analysis (TGA) following an air dielectric barrier discharge (DBD) plasma treatment. The results were then supplemented and confirmed by scanning electron microscopy (SEM), dynamic contact angle analysis (DCAA), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) measurements. After exposure to the DBD plasma at a pre-determined power level, TGA analysis showed that the residual rates retained by the PBO composites decreased, which meant an increase in the amount of resin coating the PBO fibers in the composites. Observations by SEM confirmed that there was more resin adhering to the treated PBO fibers and the wetting behavior of resin on the fibers was greatly improved. Meanwhile, DCAA for the treated fibers showed a significant enhancement in fiber surface free energy. XPS and AFM were performed in order to reveal any variations in fiber surface activity and surface morphology resulting from the surface treatment. The resulting data showed that increases in oxygen-containing polar groups and surface roughness on the plasma-treated PBO fibers contributed to the above improved wetting behavior. With comprehensive analyses, it was concluded that TGA could be used as a supporting method assessing the surface wettability of PBO fibers before and after air DBD plasma treatment.

A nanocomposite with soluble high-performance poly(phthalazinone ether sulfone ketone) (PPESK) as matrix and multi-walled carbon nanotube buckypaper (MWCNT-BP) as reinforcement was fabricated by hot-press processing. The morphologies, dynamic and static mechanical behavior, thermal stability of the MWCNT-BP/PPESK composites were studied using scanning electron microscope (SEM), dynamic mechanical analyzer (DMA) and thermogravimetric analyzer (TGA). SEM microphotographs revealed a high impregnation degree of the MWCNT-BP/PPESK composites. Dynamic and static mechanical analysis revealed that the nanocomposites possessed high storage modulus, and good retention rate of mechanical strength even at 250 °C, which is mainly attributed to satisfied impregnation and strong interactions between MWCNT-BP and PPESK. Thermogravimetric analysis exhibited that the nanocomposites had excellent thermal stability. These investigations confirm that MWCNT-BP can be effectively used to manufacture high-loading CNT/PPESK composites with improved properties.

Monitoring air pollution at a city scale is essential for controlling urban air pollution in cities, especially megacities, in China. In this paper, data for 1 city center site and 5 paired (stands and non-forested) PM2.5 monitoring sites across urban-rural areas in Beijing were collected, and air PM2.5 and influential factors were analyzed. The results showed that the mean value of PM2.5 (February to December 2013) was lower in the stands (67.00 μ gm �3 ) than in the non-forested sites (78.02 μ gm �3 ). The diurnal variation was a bimodal double-dip type, and the average daily PM2.5 was lower in the vegetation areas than in the non-vegetation areas in both Changping Dingling (vegetation) and Changping town (non-vegetation) and showed day > night. In the typical pollution process, accompanied by an increase or decrease in PM2.5 and air quality index values, the higher the PM2.5, the lower the wind speed. PM2.5 in the vegetation areas lagged behind PM2.5 in the non-vegetation areas on typical sunny days but not on typical rainy and windy days. On typical sunny days, the variation of PM2.5 in the vegetation areas was less than that in the non-vegetation areas. PM2.5 did not change significantly under rainy conditions and before a rain, but the variation was smaller after a

This paper studies the event-triggered control problem for networked switched systems with actuator saturation. An event-triggering strategy is developed based on discrete event-triggered samplings. By which, a waiting time is first ensured to avoid the Zeno-like behavior, and then the data transmission is carried out once a desired performance-dependent condition is satisfied. According to the implementation of the triggering strategy and considering the impacts of transmission delay and actuator saturation, a time-delay closed-loop switched system is developed. Subsequently, sufficient conditions to ensure stability of the closed-loop system are derived by making use of the average dwell time and multiple Lyapunov functions method. In particular, since the waiting time, periodic sampling instants, data updating instants and switching instants may be coupled with each other, typical cases are discussed thoroughly to analyze the system stability. Moreover, together with the estimation of domain of attraction, sufficient conditions for the design of the desired state-feedback sub-controller gains and event-triggering parameters are presented. Finally, the effectiveness of the proposed method is verified by numerical simulations.

We analyzed fluctuation in Beijing’s air quality over 328 days, based on air quality grades and air quality data from 35 atmospheric monitoring stations. Our results show the air over Beijing is subject to pollution 152 days of the year, or 46.34 %. Among all pollutants, fine particulates, solid or liquid, 2.5 μm or less in size (PM2.5), appeared most frequently as the primary pollutant: 249 days, or 76 % of the sample year (328 days). Nitrogen dioxide (NO2) and coarse particulates (PM10) cause the least pollution, appearing only 7 and 3 days, or 2 and 1 % of the sample year, respectively. In Beijing, fine particulates like PM2.5 vary seasonally: 154.54 ± 18.60 in winter > 145.22 ± 18.61 in spring > 140.16 ± 20.76 in autumn > 122.37 ± 13.42 in summer. Air quality is best in August and worst in December, while various districts in Beijing experience different air quality. To be specific, from south to north and from west to east, air quality tends to improve. Meteorological elements have a constraining effect on air pollutants, which means there is a linear correlation between the air quality index and humidity, rainfall, wind speed, and temperature. Under a typical pollution scenario, the higher the air quality index (AQI) value, the lower the wind speed and the greater the relative humidity; the lower the AQI value, the higher the wind speed and lower the relative humidity. Analysis of influencing factors reveals that the air pollution is mainly particulate matter produced by burning coal, vehicle emissions, volatile oils and gas, fast development of food services, emissions from the surrounding region, and natural dust clouds formed in arid areas to the northwest. Topography affects the distribution of meteorological conditions, in turn varying air quality over the region from one location to another. Human activities also exercise impact on urban air quality with dual functions.

以北京西山不同海拔梯度油松人工林为研究对象，对油松林PM2.5浓度变化和叶片PM2.5吸附量进行分析，并应用电子显微镜对不同海拔油松叶表面微形态特征进行观察，阐释叶片吸附PM2.5差异。结果表明：随着海拔升高PM2.5质量浓度逐渐降低，不同海拔油松林PM2.5质量浓度日变化均呈典型的双峰曲线，7：00和19：00是一天的两个峰值，最小值出现在13：00-15：00左右；从不同月份看，不同海拔油松林PM2.5质量浓度最高值出现在冬季的2月，最低值在8月；不同海拔油松林PM2.5质量浓度全年均值为84 m（（102.28±18.44）μg/m3）> 110 m（（94.18±18.34）μg/m3）> 160 m（（81.53±19.23）μg/m3）> 230 m（（75.39±15.71）μg/m3）；随着海拔升高单位叶面积PM2.5吸附量逐渐减小，每升高50 m，单位叶面积PM2.5吸附量降低23.25%，每公顷PM2.5吸附量下降26.43%，不同海拔油松林每公顷PM2.5吸附量全年均值为84 m（（8.61±1.08）kg/hm2）> 110 m（（7.30±0.94）kg/hm2）> 160 m（（6.35±0.99）kg/hm2）> 230 m（（4.34±1.14）kg/hm2）；处于低海拔的油松叶表面较粗糙，气孔内部和周围聚集大量颗粒物，在叶面形态上更有利于吸附PM2.5，高海拔则相反。高海拔空气质量优于低海拔，低海拔的植物吸附颗粒物多于高海拔。研究结果可为城市造林和森林净化大气提供数据支持。

The use of novel aromatic diamine containing phthalide structure (BAPP) as curing agent of diglycidylether of bisphenol A (DGEBA) epoxy resin has been studied. BAPP can react with epoxy monomers by an epoxy-amine condensation mechanism, which renders phthalide cardo incorporate into the network structure of the thermoset. The curing behavior and kinetics have been investigated by differential scanning calorimetry (DSC) and the kinetic analysis of non-isothermal cure shows that autocatalytic model is suitable to describe the cure mechanism. The thermal–mechanical properties have been determined with dynamic mechanical analysis (DMA) and the activation energies for relaxation were calculated according to the Arrhenius law. Thermogravimetric analysis exhibits a lower initial decomposition temperature, decreased rate of decomposition and higher char yield compared with DGEBA cured with commercially available 4,4′-diaminodiphenylsulfone (DDS).

Electromagnetic interference ( EMI) originated from radio stations to various electronic appliances and devices is an increasingly serious problem, and there are significant interests in the development of light-weight, high-efficiency materials for EMI shielding. Herein we report novel carbon nanotube (CNT)composite films synthesized by a simple spray and vacuum-filtration method. The film containing 30 wt%single-walled CNTs demonstrates high electrical conductivity up to 20,000 S/m and excellent EMI shielding effectiveness 65 dB, with ~130 μm in thicknesses and 0.011 g/cm² in areal density. The composite films are stiffer, stronger and more ductile than neat MWCNT film, i.e. 17.4 versus 3.3 MPa in tensile strength. Our films are sufficiently smooth, tough and flexible, which allow themselves to attach onto any complex curved surface. SWCNTs play an essential role in achieving such exceptional functional and mechanical performance; both SWCNTS and MWCNTS need to be well disentangled prior to the filtration. The composite films would have a wide range of engineering applications, i.e. production of conventional composite laminates due to their porous structure Refereed/Peer-reviewed