乳胶基质体系分散相粒度分布研究

乳胶基质分散相的粒径对乳化炸药的稳定性,爆轰性能都有很大的影响。本文利用两种测试手段分析乳胶基质的粒径分布与乳化搅拌剪切速度的关系,实验结果表明:乳胶基质分散相粒径大小,随着搅拌剪切速度的增加而减小;乳胶基质乳化搅拌的临界剪切速度为1500 r/min;剪切速度越高,乳胶基质分散相粒径平均值越小,分布越均匀。     

双重非均匀子群参数制作研究

弥散颗粒燃料元件中燃料颗粒以随机形式弥散在基体中,难以获得确定几何。同时由于共振自屏现象的存在,呈现出一种双重非均匀系统。当前均匀系统产生的共振积分在双重非均匀系统中使用时,会在较低的共振能群产生一定的共振计算误差。为满足现有组件计算程序直接进行双重非均匀性共振计算的需求。基于Sanchez-Pomraning模型下的特征线固定源计算方法,建立一套双重非均匀共振积分表,最后结合子群方法实现随机介质燃料元件的共振计算。数值结果表明,考虑双重非均匀性产生的积分表,在相同的输运条件下和积分表的适用范围内,由子群共振部分对keff计算带来的绝对偏差能保持在200 pcm内。该工作的意义是对于一些不宜改动的传统组件程序,如HELIOS,通过在线修改共振积分表和子群参数,从而使其直接进行弥散颗粒燃料问题的计算成为可能。     

基于复合萃取技术-超高效液相色谱-串联三重四极杆质谱法同时测定谷物及其制品中10种真菌毒素

目的 建立超高效液相色谱-串联三重四极杆质谱法(ultra performance liquid chromatography-tandem with triple quadrupole mass spectrometry,UPLC-MS/MS)同时测定谷物及其制品中的10种真菌毒素的检测方法。方法 以0.1%甲酸-80%乙腈水为提取溶剂,经过涡旋、振荡提取后,加入Supel QuE z-sep+作为净化剂进行初级净化,离心后的上清液过PRiME HLB固相萃取柱二次净化,经UPLC-MS/MS测定,质谱采用多反应监测模式定性,基质匹配标准溶液外标法定量。结果 10种真菌毒素在谷物中的检出限为0.10～10.00μg/kg,定量限为0.35～20.00μg/kg。在玉米、花生、大米3种谷物基质中的回收率为73.2%～98.1%,相对标准偏差为1.3%～9.3%。结论 该方法的灵敏度满足国家标准对真菌毒素的限量要求,实验操作简便快速,成本较低,定性定量分析可靠,适合谷物中真菌毒素的多组分高通量快速分析测定。     

分散相形态对MWCNTs/PBT/HDPE共混物摩擦磨损性能的影响

为研究分散相不同形态结构对共混物的力学及摩擦学行为的影响,以PBT/HDPE共混体系为研究对象,通过挤出过程的拉伸牵引作用制备分散相为纤维结构的共混物;通过控制注射成型温度,调控PBT分散相的不同形态结构,研究其对摩擦学性能的影响及其抗磨损机制;通过在分散相中加入润滑粒子多壁碳纳米管(MWCNTs),探讨MWCNTs的...     

基于聚合物分散液晶的图案化柔性智能窗户

聚合物分散液晶(PDLC)在投影显示和智能窗户等领域具有广泛的应用,将器件实现图案化和柔性化能够进一步拓展其应用场景。本文提出了一种采用单步紫外曝光的方式制备图案化的PDLC柔性智能窗户。采用PET-ITO作为柔性基板制备液晶盒,并于器件上表面放置一层有特定紫外衰减率的图案化掩膜板进行紫外固化,线宽为120μm的图案能够清晰分辨。本文对图案化器件的不同区域的电光特性进行了研究,实验结果表明：采用高紫外光固化区域的PDLC具有较高的阈值电压和饱和电压。高紫外固化区域和低紫外固化区域上升时间分别为4.1ms和15.4ms,下降时间分别为14.1ms和33.7ms,满足智能窗户应用需求。通过施加不同的外加电场,该图案化智能窗户能够呈现全散射态、全透明态和图案化透明展示态3种模式。最后本文展示了器件处于平面状态和弯曲状态下施加不同驱动电压时该柔性智能窗户的展示效果。本研究表明采用上述单步紫外曝光方式制备的图案化PDLC柔性器件具有工艺简单、成本低、精度高等优势,有利于其在定制化图案的柔性智能窗户领域的广泛应用。     

分散固相萃取-气相色谱-串联质谱法同时测定母乳中24种有机氯类农药

目的 利用液液萃取-分散固相萃取-气相色谱-串联质谱技术构建母乳中24种有机氯类农药的分析方法。方法 母乳样品用正己烷-丙酮(3:1,V:V)超声提取,提取液冷冻除脂后经N-丙基乙二胺 (primary secondary amine, PSA)作为分散固相萃取剂净化,净化液氮吹复溶后采用气相色谱-串联质谱法(Gas Chromatography-Tandem Mass Spectrometry,GC-MS/MS)检测,内标法定量。 结果 24种有机氯农药在考察的浓度范围内线性关系良好,相关系数r²≥0.99;方法检出限为0.002~0.500μg/kg,定量限为0.006~1.500μg/kg;24种目标物在高中低三个不同加标浓度下的回收率为87.1%~129.0%,相对标准偏差为1.9%~13.9%。 结论 该方法操作便捷、定量准确、灵敏度高,能够满足母乳样品中24种有机氯农药残留的快速检测分析需求,为监测母乳及婴儿体内的有机氯农药含量提供方法学参考。     

Error tracking mode AC current waveform control method for three-phase self-commutated voltage source power converters

A novel design theory for a three-phase self-commutated power conversion system (PCS) to perform as an ac current source is proposed. In this new ac current waveform control method termed error tracking mode, the switching instructions of main devices are decided only by the error function of ac current at every data sampling time that comes in a constant period. The performance is theoretically evaluated. Simulation by SPICE also is executed and the characteristics are inspected. Error tracking mode has the following attractive features. It can treat two arbitrary current waveforms as target functions of two-phase arbitrary ac currents. The error between actual ac current value and the objective function value can be controlled and guaranteed to be less than an arbitrary value, which is given beforehand. All control components can be digitized. The minimum continuous on and off time of main devices is guaranteed in advance. No special starting control is necessary because actual ac currents are guaranteed to start tracking the target functions automatically. Error tracking mode makes contributions to improve precision in current control and to reduce current harmonics of self-commutated voltage source power converters.     

The Role of Nanosize Particles of Uranium Oxide in the Adsorption/Reaction of Methanol Over U3O8/MCM-48: FTIR Study

The surface species formed over MCM-48, U₃O₈ and U₃O₈/ MCM48 catalysts during the adsorption/reaction of methanol were monitored using FTIR spectroscopy, in order to get an insight into the high catalytic activity exhibited by the nanosize crystallites of uranium oxide dispersed in MCM-48. The results of this in situ study revealed that the title catalysts exhibited a distinct behavior for adsorption and subsequent reaction of methanol. Thus, while the room temperature adsorption over bulk U₃O₈ resulted in the formation of formate complex and oxymethylene species, the interaction over MCM-48 resulted in simultaneous and instant formation of surface methoxy groups and dimethyl ether. On the other hand, the exposure of methanol over U₃O₈/MCM-48 under similar conditions resulted in the appearance of intense IR bands due to surface-adsorbed (–OCH₂)_n species, where n1, in addition to those of formate complexes, oxymethylene and methoxy groups. The role of the above-mentioned intermediate species in the formation of different reaction products is discussed in brief.     

Continuous and dispersed phase coefficients for heat and mass transfer involving single-file drops

An attempt has been made in this paper at modelling analogous situations of heat or mass transfer involving single-file drops in liquid-liquid systems. Experimental data on continuous and dispersed phase coefficients have been correlated.     

A novel nanoemulsification method of stirring at the Θ-point with the tocopherol-based block co-polymer nonionic emulsifier PPG-20 Tocophereth-50

Nanoemulsions have recently become increasingly important as potential vehicles for the controlled delivery of cosmetics and for the optimized dispersion of active ingredients in particular skin layers. The preparation of conventional nanoemulsions requires mainly high‐pressure homogenization, which is unproductive and requires high energy due to its lower efficiency, limiting their practical applications. In order to solve these problems novel nanoemulsions were studied using a model system of pseudo‐ternary water/emulsifier/paraffin oil. Nanoemulsions were prepared by stirring a mixture of the tocopherol‐containing block co‐polymer emulsifier PPG‐20 Tocophereth‐50, paraffin oil, and distilled water at the Θ‐point using weight fractions of the dispersed phase (φ) of 0.31 to 0.82 and an emulsifier content of 1.0 to 9 wt.%. The emulsifying property of PPG‐20 Tocophereth‐50 in nanoemulsions was compared with that of the conventional emulsifiers Tocophereth‐43, a mixture of polysorbate 60 and sesquioleate (3/1), and phospholipids. Also the emulsifying property of PPG‐20 Tocophereth‐50 in the more hydrophilic oils caprylic/capric triglyceride and octyldodecanol was compared with that in paraffin oil. The stability and morphology of the resulting nanoemulsions were studied by visual inspection, optical microscopy, particle size analysis, and cryo‐scanning electron microscopy. In the nanoemulsion systems containing caprylic/capric triglyceride and octyldodecanol, respectively, as an oil phase PPG‐20 Tocophereth‐50 showed emulsification properties similar to those in paraffin oil. The conventional emulsifiers Tocophereth‐43, a mixture of polysorbate 60 and sesquioleate (3/1), and phospholipids did not give nanoemulsions with high‐speed stirring. The block co‐polymer nonionic emulsifier PPG‐20 Tocophereth‐50 was found to produce stable nanoemulsions of mean droplet diameters ranging from 204 to 499 nm. The emulsification method of high‐speed stirring at the Θ‐point using PPG‐20 Tocophereth‐50 was found to be very effective for the preparation of stable nanoemulsions useful for applications in skincare cosmetics, cosmeceuticals, and drugs.