航天相机热实验测试系统设计

为了检测航天相机在高低温环境中的电子学性能及可靠性,针对某型号航天相机地面热实验测试需求,设计开发出了一种热实验测试系统,详细介绍了系统的软硬件设计方案及控温策略。系统使用人机交互界面实现热控策略,能实时完成最高80个测试点(160个温度传感器及80路加热器)的控温任务,可以在－30℃～＋50℃范围内对航天相机进行全方位的温度监控,最高控温精度达到0.5℃。经过实际测试验证,系统具有很好的稳定性,能满足航天相机地面热实验的测试需求,工程应用价值高。     

Thermal-Induced Dimerization Cyclization of Ethyl N-(Styrylcarbamoyl)acetates: Formation of 4-Hydroxy-2(1H)-pyridone-3- carboxamide Derivatives

Thermal-induced dimerization cyclization of ethyl N-(styrylcarbamoyl)acetate derivatives has been investigated, leading to 4-hydroxy-2(1H)-pyridone-3-carboxamide derivatives with good yields in diphenyl ether on 200–210 °C. Ethyl N-(styrylcarbamoyl)acetate derivatives readily provided the intermolecular cyclization products 4-hydroxy-2(1H)-pyridone-3-carboxylates on reflux in xylene. In addition, several related 3-acetyl-4-hydroxy-5-phenylpyridin-2(1H)-ones have been prepared. It provided an efficient preparation of 4-hydroxy-2(1H)-pyridone-3-carboxamide derivatives.     

Synthesis,Characterization, and Surface Properties of Cationic Gemini Surfactants

New pyridinium gemini surfactants have been synthesized by esterification of renewable fatty acids with mercaptoethanol furnishing respective esters (mercaptomethyl decanoate, mercaptomethyl dodecanoate, mercaptomethyl tetradecanoate, mercaptomethyl hexadecanoate) followed by their subsequent treatment with 4-dimethyl amino pyridine resulting in the formation of title gemini surfactants: 1-(5-(decanoyloxy)-2-hydroxypentyl)-4-((5-(decanoyloxy)-2-hydroxypentyl)dimethyl ammonio)pyridin-1-ium chloride (9), 1-(5-(dodecanoyloxy)-2-hydroxypentyl)-4-((5-(dodecanoyloxy)-2-hydroxypentyl)dimethyl ammonio)pyridin-1-ium chloride (10), 1-(5-(tetradecanoyloxy)-2-hydroxypentyl)-4-((5-(tetradecanoyloxy)-2-hydroxypentyl)dimethyl ammonio)pyridin-1-ium chloride (11), and 1-(5-(hexadecanoyloxy)-2-hydroxypentyl)-4-((5-(hexadecanoyloxy)-2-hydroxypentyl)dimethyl ammonio)pyridin-1-ium chloride (12). Their identifications are based on infrared, ¹H NMR, ¹³C NMR, distortionless enhanced polarization transfer, co-relational spectroscopy (COSY), and mass spectral studies. Their surface active properties are also evaluated on the basis of surface tension and conductivity measurements. Thermal stability of these long chain cationic gemini surfactants have been measured by thermal gravimetric analysis under nitrogen atmosphere.     

Effects of Magnetic Nanofluid Fuel Combustion on the Performance and Emission Characteristics

Although the compression ignition engines are a significant source of power, their detrimental emissions create considerable problems to the environment as well as to humans. The objective of the present experimental investigation is to examine the effects of the magnetic nanofluid fuels on combustion performance characteristics and exhaust emissions. In this regard, the Fe₃O₄ nanoparticles dispersed in the diesel fuel with the nanoparticle concentrations of 0.4 and 0.8 vol% were employed for combustion in a single-cylinder, direct-injection diesel engine. After a series of experiments, it was demonstrated that the nanoparticle additives, even at very low concentrations, have considerable influence in diesel engine characteristics. Furthermore, the results indicated that the nanofluid fuel with nanoparticle concentration of 0.4 vol% shows better combustion characteristics in comparison with that of 0.8 vol%. Based on the experimental results, NO _x and SO₂ emissions dramatically reduce, while CO emissions and smoke opacity noticeably increase with increasing the dosing level of nanoparticles.     

聚四氟乙烯和石墨对聚醚酰亚胺摩擦学性能的影响

将聚四氟乙烯(PTFE)和石墨两类减摩耐磨填料填充到聚醚酰亚胺(PEI)中,表征其摩擦性能,利用扫描电子显微镜分析了磨损表面的显微结构,并分析了磨损机制.研究结果表明,PTFE和石墨的填充明显改善了PEI的摩擦磨损性,摩擦系数降低到0.3以下(纯PEI的摩擦系数为0.41),磨损率降低了3个数量级.在PTFE体系中,PTFE质量分数为10%时,PEI基共混材料的摩擦系数最低为0.23;而在质量分数为15%的石墨体系中,PEI基共混材料摩擦系数最低为0.27.磨损率随着填料含量的增加而逐渐下降,在填料质量分数为20%之后,摩损率下降平缓.因此PTFE和石墨的填充对PEI的摩擦学性能起到了很好的改善作用,而且PTFE比石墨的改善效果更优益.共混物的机械性能测试结果表明,在填料质量分数为5%~15%时,共混物具有良好的机械性能.     

含硼杂原子Na-B-ZSM-5分子筛对甲醇脱氢制甲醛反应的催化性能

以白炭黑为硅源、硼酸为硼源、NaOH为碱源、四丙基溴化铵(TPABr)和1,6-己二胺(HMDA)混合模板剂,采用水热合成法制备含硼杂原子Na-B-ZSM-5分子筛,用XRD、SEM、FT-IR、UV-vis、11B MAS NMR、NH3-TPD等方法对其进行表征。在连续流动常压固定床反应器上评价Na-B-ZSM-5分子筛对甲醇脱氢制甲醛反应的催化性能,考察n(Si)/n(B)、n(Na2O)/n(SiO2)、晶化温度和晶化时间等制备参数以及反应温度和质量空速等工艺参数对催化性能的影响。结果表明,硼进入了分子筛的骨架结构中,存在与B酸中心有关的骨架四配位硼和与L酸中心有关的骨架三配位硼,Na-B-ZSM-5分子筛含有较多的弱酸位和少量的中强酸位。催化剂的最佳制备参数为n(Si)/n(B)比值为7.5、n(Na2O)/n(SiO2)比值为0.14、晶化温度170℃、晶化时间48 h。Na-B-ZSM-5(7.5)分子筛在反应温度550℃、质量空速1.85 h-1的反应条件下对甲醇的转化率为62.97%,甲醛的选择性为68.86%。     

Determination of four sulfonylurea herbicides in tea by matrix solid‐phase dispersion cleanup followed by dispersive liquid–liquid microextraction

Matrix solid‐phase dispersion combined with dispersive liquid–liquid microextraction has been developed as a new sample pretreatment method for the determination of four sulfonylurea herbicides (chlorsulfuron, bensulfuron‐methyl, chlorimuron‐ethyl, and pyrazosulfuron) in tea by high‐performance liquid chromatography with diode array detection. The extraction and cleanup by matrix solid‐phase dispersion was carried out by using CN‐silica as dispersant and carbon nanotubes as cleanup sorbent eluted with acidified dichloromethane. The eluent of matrix solid‐phase dispersion was evaporated and redissolved in 0.5 mL methanol, and used as the dispersive solvent of the following dispersive liquid–liquid microextraction procedure for further purification and enrichment of the target analytes before high‐performance liquid chromatography analysis. Under the optimum conditions, the method yielded a linear calibration curve in the concentration range from 5.0 to 10 000 ng/g for target analytes with a correlation coefficients (r²) ranging from 0.9959 to 0.9998. The limits of detection for the analytes were in the range of 1.31–2.81 ng/g. Recoveries of the four sulfonylurea herbicides at two fortification levels were between 72.8 and 110.6% with relative standard deviations lower than 6.95%. The method was successfully applied to the analysis of four sulfonylurea herbicides in several tea samples.     

Simultaneous determination of seven phthalic acid esters in beverages using ultrasound and vortex‐assisted dispersive liquid–liquid microextraction followed by high‐performance liquid chromatography

A sensitive, rapid, and simple high‐performance liquid chromatography with UV detection method was developed for the simultaneous determination of seven phthalic acid esters (dimethyl phthalate, dipropyl phthalate, di‐n‐butyl phthalate, benzyl butyl phthalate, dicyclohexyl phthalate, di‐(2‐ethylhexyl) phthalate, and di‐n‐octyl phthalate) in several kinds of beverage samples. Ultrasound and vortex‐assisted dispersive liquid–liquid microextraction method was used. The separation was performed using an Intersil ODS‐3 column (C₁₈, 250 × 4.6 mm, 5.0 μm) and a gradient elution with a mobile phase consisting of MeOH/ACN (50:50) and 0.2 M KH₂PO₄ buffer. Analytes were detected by a UV detector at 230 nm. The developed method was validated in terms of linearity, limit of detection, limit of quantification, repeatability, accuracy, and recovery. Calibration equations and correlation coefficients (> 0.99) were calculated by least squares method with weighting factor. The limit of detection and quantification were in the range of 0.019–0.208 and 0.072–0.483 μg/L. The repeatability and intermediate precision were determined in terms of relative standard deviation to be within 0.03–3.93 and 0.02–4.74%, respectively. The accuracy was found to be in the range of –14.55 to 15.57% in terms of relative error. Seventeen different beverage samples in plastic bottles were successfully analyzed, and ten of them were found to be contaminated by different phthalic acid esters.     

Comparison of different types of outlet frits in slurry‐packed capillary columns

Fused‐silica capillary columns for high‐performance liquid chromatography with 320 and 250 μm inner diameter were prepared by slurry packing with 5 and 3 μm Nucleosil C₁₈ stationary phase. Different types of mechanical and monolithic outlet frits were used and their influence on the resulting column performance was evaluated. Columns with quartz wool exhibited symmetrical peaks and low theoretical plate height, and the preparation time was short. The performance of monolithic frits varied based on type of monolith, length of the frit, and silanization procedure. The best frit performed similarly to the quartz wool ones, but the preparation took several hours. Their main advantage lies in the possibility of on‐column detection, because the detection window can be burnt immediately behind the frit.     

Multiresidue analysis of quinolones in water by ultra‐high perfomance liquid chromatography with tandem mass spectrometry using a simple and effective sample treatment

A rapid and simple analytical method has been developed for the determination of 19 quinolones in environmental water samples using ultra high performance liquid chromatography with tandem mass spectrometry. Chromatographic and detection conditions have been optimized and the separation was achieved in less than 4 min. The separation was carried out using a new‐generation column filled with superficially porous particles, resulting in lower backpressure and better resolution than totally porous particle columns. The quinolones were detected by electrospray ionization in positive mode using multiple‐reaction monitoring mode for acquisition. A sample treatment based on liquid–liquid extraction and phase separation via salting‐out was employed to achieve a fast and simple extraction that enables the multiresidue analysis. The method has been validated for an environmental well water sample from a mountain area. Very low limits of detection (between 10 and 90 ng/L) with relative standard deviations lower than 16.5% and recoveries higher than 73% were achieved. Moreover, well waters from different origins (mountain and coast areas and irrigated land) have been evaluated and similar results were obtained.