Synthesis and dielectric properties of polystyrene‐clay nanocomposite materials

Polystyrene‐clay nanocomposite (PsCN) materials were synthesized and their properties of crystallinity, thermal behavior, and dielectric characteristics were investigated. A polymerizable cationic surfactant, [2‐(dimethylamino)ethyl]triphenylphonium bromide, was used for the intercalation of montmorillonite (MMT). The organophilic MMT was prepared by Na⁺‐exchanged MMT and ammonium cations of a cationic surfactant in an aqueous medium. Organophilic styrene monomers were intercalated into the interlayer regions of organophilic clay hosts followed by a free‐radical polymerization. Exfoliation to 2 wt % MMT in the polystyrene (PS) matrix was achieved as revealed by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). Thermal properties by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were also studied. The dielectric properties of PsCNs in the form of film with clay loading from 1.0 to 5.0 wt % were measured under frequencies of 100 Hz–1 MHz at 25–70°C. A decreased dielectric constant and low dielectric loss were observed for PsCN materials. The dielectric response at low frequency that originated from dipole orientation was suppressed due to the intercalation of clay materials. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1368–1373, 2004     

提高腺病毒对肿瘤细胞转染效率的药物效果评价

为了解决在肿瘤基因治疗中腺病毒载体介导的转染细胞效率低的问题,高效、低毒的转染试剂为其提供了一条新途径.采用正十二烷基-β-D-麦芽糖苷(n-Dodecyl-β-D-Maltoside,DDM)、DC-Chol、SDS联合腺病毒e GFP-Ad转染肝癌细胞Hep G2、食管癌细胞EC109及人正常肝细胞L-02与食管正常细胞Het-1A,48 h后观察绿色荧光蛋白表达情况并计阳性细胞率,评价联合转染试剂处理提高e GFP-Ad转染肿瘤细胞的效率.实验结果表明,DDM(3μg/m L)、DC-Chol(1 000μg/m L)、SDS(0.5μg/m L)联合e GFP-Ad转染肿瘤细胞Hep G2和EC109的效率分别可达85%和78%、80%和76%、45%和41%,与单独e GFP-Ad相比,转染效率分别提高16倍和14.6倍、15倍和14.2倍、8倍和7.2倍;且与正常细胞相比,DDM能显著提高对肿瘤细胞的转染效率,二者差异具有高度统计学意义.作为非脂质体类试剂,DDM能显著提高腺病毒对肿瘤细胞的转染效率,为进一步提高腺病毒介导的肿瘤基因治疗提供有效方法与技术参考.     

Experimental Study of Electrodes Parameters Effects on Small Diffusion Combustion Flame

To study the configuration and conductivity effects on micro?scale methane?air flames by electric field and iron wind, different electric field forces and iron winds are generated by needle, circle and...     

抱罐车优化创新设计与应用

针对抱罐车在制造、使用过程中易出现的各种问题,提出相对应的优化设计方法,并予以应用。证明经过创新优化设计后的抱罐车相应性能有了显著提高,指出模块化、智能化、节能、环保、远程监控等将是抱罐车的发展趋势。     

Non-coalescence and chain formation of droplets under an alternating current electric field

The dynamic behaviors of two droplets and droplet cluster under an alternating current (AC) electric field are investigated. Two droplets generally undergo transformation from complete coalescence to partial coalescence and finally to non-coalescence as the electric capillary number Ca_p increases. The critical electric capillary number Ca_pc for complete coalescence in the AC electric field remains unchanged and is twice as large as that in the direct current (DC) electric field when the frequency f ≥ 250 Hz. Charge transfer and reversal of electric field result in the reversal of the direction of electric force, which is the fundamental mechanism of non-coalescence of two droplets and chain formation in droplet cluster. The number of rebounds dramatically increases as f increases, promoting the stability of droplet chain. The droplet chains in the high-frequency AC electric field are longer and more stable than those in the low-frequency AC electric field.     

空调负荷二阶等效热参数模型参数辨识方法

空调负荷是最具潜力的需求侧资源之一.然而,由于建筑环境、用户偏好等因素的差异,空调负荷具有明显的异质性,脱离实际场景建立空调负荷异质性聚合模型,难以准确获取其聚合功率及响应潜力.在具体应用场景下,搭建了实际空调负荷集中控制系统,并在实际空调系统支持下,提出计及空调负荷二阶等效热参数模型参数时变特性的参数辨识方法.通过最小化二阶等效热参数模型仿真温度与实测温度误差,同时考虑参数的时变特性,建立优化模型,获得二阶等效热参数模型参数.算例结果表明,所提方法能够建立较为准确的空调负荷二阶等效热参数模型.     

Research progress on preparation of biomass-derived porous carbon and its adsorption of pharmaceuticals in wastewater

The rapid development of urban modernization and industrialization has caused increasingly serious pollution to the environment, especially water contamination. In recent years, the content of pharmaceuticals in industrial wastewater has increased year by year, and the pollution should not be ignored any more. Therefore, the development of new porous materials for the adsorption and separation of pharmaceutical molecules in wastewater has become a current research hotspot. This article summarizes the recent research on the adsorption and separation of pollutants in wastewater by biomass-derived porous carbons (biochars). First, it briefly introduces the treatment methods of pollutants in wastewater, and mainly focuses on the preparation and modification of biochars. Combined with the surface chemical properties and pore structure of the carbon materials, this paper summarizes and prospects the adsorption properties of biochar to pharmaceuticals.     

旋转扫描结构光的三维检测系统及其标定

针对传统平移扫描检测系统的缺陷,提出了一种基于旋转扫描线结构光的三维检测与重构系统及对应的系统参数标定方法,建立了点云数据获取模型。被测物体通过旋转实现与线结构光间的相对运动,得到被测物体的外表面二维图像。系统标定获得图像坐标与世界坐标间的转换关系,得到被测物体的三维坐标信息及数字模型。由实验可知,相机的标定精度为0.2 mm,原理样机进行物体测量的精度为0.1 mm。实验证明该系统检测精度高,具有可行性。     

形变与热处理对CuCr合金中Cr相形貌及合金性能的影响

研究了CuCr合金在不同形变与热处理制度下，组织中Cr相形貌、合金力学性能及导电性能的变化。结果表明：当变形量达到70％时，合金中的Cr粒子产生严重的变形，且有开裂现象。在随后高温热处理过程中开裂的Cr粒子发生熔断和球化。适当的形变与热处理能改善CuCr合金的力学性能与导电性能，并从微观组织方面对其原因进行了分析。     

DISTRIBUTION OF Al AND Ce BETWEEN Ag AND Fe

利用Ag,Fe两种金属几不互溶的特性,测定了Al在Ag与Fe间的分配,并进一步测定了Ag中ca对Al的相互作用系数f_(Al)~(Ca)及算出了相互作用参数e_(Al)~(Ca),e_(Ca)~(Al),用同样方法初步测定了Ce在Ag与Fe间的分配。根据我们的实验结果还对Al的脱氧常数进行了修正。