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Volatile organic compounds (VOCs) are important precursors of ground-level ozone and secondary organic aerosol, and its monitoring and emission control are very necessary for national environmental protection. Under the guide of policy and demand, on-board monitoring technology for VOCs becomes popular. The on-board monitoring technology has high spatial and temporal resolution and high efficiency for VOCs monitoring, which has become the hotspot technology in VOCs rapid monitoring filed. However, when there are many target compounds with the same quality, there is only one peak in the mass spectrum for these compounds obtained by the traditional on-board monitoring technology with the method of single mass spectrometer, which reduces the detection precision. Therefore, dual mode VOCs on-board monitoring system including SPI-TOF MS model and fast GC-SPI-TOF MS model were established by developing fast gas chromatography (GC)-single photon ionization (SPI)-time of flight mass spectrometry (TOF MS) devices combing with mobile car. When VOCs were monitored by the on-board monitoring system, the SPI-TOF MS mode was firstly used to analyze the VOCs in air by the process of driving, and the results of real-time qualitative quantitative analysis for each point of VOCs were obtained. When high value point of VOCs pollution was found, the car was stopped, and the analysis mode was switched to GC-SPI-TOF MS to determine whether there were compounds with the same m/z, which aimed at ensuring the speed of onboard monitoring and improving the detection accuracy at the same time. During the research, the performance of the system was evaluated by PAMs and TO-15 standard gas. The results showed that the system had a good detection ability for isomers and co-effluent components from GC. The reproducibility error of signal intensities were lower than 5.00% for 92% compounds by both SPI-TOF MS mode and GC-SPI-TOF MS mode, the reproducibility error of retention time was lower than 0.30% for 100% compounds, and the detection limits for typical VOCs species were between 0.28×10-9 and 8.50×10-9, which were better than the national or local testing standard. The system was applied to VOCs monitoring at an industrial park. With high time resolution (in seconds) monitoring ability, m/z 120 was identified for normal propyl benzene which came from suspicious enterprises B. Rapid GC-SPI-TOF MS is a quick and accurate monitoring equipment for VOCs, which not only improves the ability of equipment for VOCs monitoring, but also provides data support for VOCs emission management and control in China.

Modified polyimides (MPIs) show great potential towards 5G communication applications, due to its excellent thermal stability, mechanical property and chemical stability as compared to most of polymers. Introducing fluoride groups or porous structure is favorable to ultra-low dielectric constant (Dk) and dielectric loss (Df). However, the cost of the fluorinated MPIs is high and their synthetic processes are complicated, and porous MPIs suffer poor mechanical properties. Also, increasing the fraction of free volume is a very effective way to lower Dk through introducing more ultra-low-Dk air component. However, most of this kind of MPIs lag far behind the fluorinated MPIs and the porous MPIs in terms of ultra-low Df, hindering the application of MPIs in high-speed communication devices. Thus, it is highly desirable to develop intrinsic ultra-low-Dk/Df MPIs at high frequency with less fluoric groups and nonporous structure. Herein, we introduce a facile and effective strategy to lower Dk and Df through introducing rigid and large sterically hindered aromatic groups into MPIs. On the one hand, their large steric hindrance effect leads to low Dk by increasing intrinsic free volume. On the other hand, the resulting highly stiff polymer chain and strong intermolecular interaction are favorable to reduce Df by inhibiting dipole orientations. Based on this strategy, the spirobifluorene groups are preferred. The as-prepared MPIs show excellent dielectric performance with low Dk of 2.74–2.76 and low Df of 0.00599 at 10 GHz, to some extent, exceeding the multiple fluorinated MPI with Dk/Df of 2.67/0.00663 at 10 GHz. [ABSTRACT FROM AUTHOR]

The paper proposed a design scheme of data collection system of dynamic electronic railway scale and mainly introduced hardware design of weighing channel which influences performance of the system. The system uses AD625 and second-order low-pass filtering circuit to make primary process for sensor signal, and uses PCI-8325B to realize AD conversion for the processed data and sends the data to front host to make software process through PCI bus, then sends the data to terminal computer through network bridge or Modem to realize unified management for the data. The test result showed that the system meets with actual application requirements of object.

Background: Actinic keratosis (AK) is a precancerous disease, caused by ultraviolet radiation (UV). Objective: To analyze the clinical and pathological characteristics of AK in four areas with different ultraviolet radiation intensities. Methods: 1188 diagnosed AK patients, from January 2000 to July 2015, in dermatology department of four hospitals were collected. The UV intensity of hospital located cities from high to low is Kunming, Yinchuan, Shenyang and Nanjing. The information comes from medical records, and the pathological types and Keratinocyte Intraepithelial Neoplasia (KIN) grades were checked by two experienced pathologists. All information was conducted a retrospective multicenter research. Results: The patients were mainly middle‐aged and elderly female, which was in direct contrast to the majority of men in European. The age of onset in Kunming group was lower than that in Yinchuan Group (p = 0.013) and Nanjing Group (p < 0.01). The course of disease in Kunming group was significantly shorter than that in Nanjing Group (p < 0.001). The lesions were almost located in the exposed area. The proportion of unexposed areas in Shenyang group was significantly higher than that in other groups (p < 0.001). There were statistical differences in pathological morphological classification among the four groups. These differences were not affected by age and gender. The number of KIN III grade patients in Shenyang group was significantly higher than that in other three groups (p < 0.05). Conclusion: The Asian patients were mainly female. The clinical characteristics of AK are closely related to UV intensity, and environmental pollution, lifestyle, religious beliefs and other factors are also related. [ABSTRACT FROM AUTHOR]

LiNi0.8Co0.1Mn0.1O2 (NCM811) has attracted increasing attention owing to its extremely high discharge capacity (>200 mA h g−1). However, poor mechanical strength, cycling stability, and rate capability impose limitations on its large-scale practical applications. Here, we report that few-layer and rod-like MXene (Ti2C3Tx) as a multifunctional additive significantly enhances the mechanical property, cycling performance, and rate capability of the Li/NCM811 cells. Thus, NCM811 added with 2.5 wt% MXene (2.5-MXene) delivers the highest discharge capacity of 209 mA h g−1 at 0.2C as well as the best rate performance with a high reversible capacity of 95 mA h g−1 at 8C. Moreover, the capacity retention of 2.5-MXene can reach 77.0% after 100 cycles at a 0.5C rate, while it is only 53.6% for pristine NCM811 without MXene (0-MXene). Such superior performances result from the effective and multifunctional MXene additive, which is helpful to establish a better conductive network, store/release Li+via cation intercalation, offer more deformation space, form a physical protection CEI layer, and suppress the M ↔ H2 phase transformation for the NCM811 electrodes. In addition, the DFT calculation indicates that the MXene additive can prohibit the irreversible Ni/Co/Mn elements' migration via the absorption process. Therefore, the few-layer/rod-like MXene can be a facile and efficient approach to enhance the mechanical and electrochemical performance of the NCM811 materials for large-scale applications in the next-generation energy density lithium-ion batteries by considering its multifunctional properties, low cost, and convenient accessibility. [ABSTRACT FROM AUTHOR]