Study on structure-property relationship of polyimide blends

Summary Three pairs of polyimide/polyimide blends (50/50 wt%) with different molecular structures were prepared by two ways, i.e. mixing of the polyamic acid precursors with subsequent imidization, and direct solution mixing of the polyimides. The blends were studied with DMA technique. The results obtained show that all the blends prepared with these two different ways are miscible, as there existed only one glass transition temperature (Tg) for all the blends. It is suggested that the miscibility of these polyimide/polyimide blends is a result of the strong inter-molecular charge-transfer interaction between the chains of their components.     

聚砜酰胺的分子量对其超滤膜性能的影响——Ⅲ.热性能

对不同分子量的PSA 材料和由其制成的超滤膜的TGA、DSC 及FTIR 研究表明,PSA 会以氢键的形式吸附水份,被吸附的水份主要以单分子形式存在,双聚或多聚的也有,但较少;并且在温度升到40℃左右将全部游离出来,在120℃左右则全部气化离开PSA。PSA 材料在400℃以上才开始分解,其耐热性能随分子量的增大而降低。凝胶浴不同对PSA 膜的晶态影响不大。     

Analysis over factors of innovation in China’s fast economic growth since its beginning of reform and opening up

The technological progress makes great contribution to the rapid economic growth of China during its past three decades of reform and opening up. An empirical analysis conducted over China’s total factor productivity certifies this conclusion but it also reveals that China’s TFP growth rate is not very high. We further explore the various stages of change of China’s total factor productivity and the causes of these changes and finally take an analytical calculation over the present flaws of China’s innovation system and offer some advices.     

充填浮选柱捕集区气含率的试验研究

通过冷模试验方法考察了充填浮选柱捕集区的气含率，经试验数据回归分析，气含率εｇ＝０．０９６Ｊｇ０．９１（Ｈｃ／Ｄ）－０．１８。并结合漂移通量的理论，确定充填浮选柱的捕集区为近似均匀鼓泡流。     

超声辐照制备SrFeO3降解苯酚光催化性能研究

采用超声辐照柠檬酸络合法制备了复合氧化物SrFeO3，以苯酚为光催化探针分子，以450W高压汞灯为光源（主波长〉410nm），研究了SrFeO3光催化性能、研究表明，经过超声辐照制备的SrFeO3光催化活性提高一倍以上。XRD、TEM、DRS表征结果表明，超声辐照制备的SrFeO3粒径均匀、分散性好、粒径较小，光吸收红移显著。探讨了超声提高催化性能的机理。     

Study on pH‐sensitive and thermosensitive polymer networks containing polyacetal segments

A series of pH‐sensitive and thermosensitive polymer networks were first obtained by copolymerization of telechelic poly(1,3‐dioxolane) (PDXL) with acrylic acid (AA), acrylamide (AM), and N‐isopropylacrylamide (NIPAM), respectively. The copolymerization of PDXL diacrylate (PDXLDA) with AA, AM, or NIPAM is expected to lead to polymer networks in which homopolymeric segments of the monomer are connected by polyacetal segments. As a combination of these two parts, these polymer networks can have some interesting physical properties. For example, the copolymer networks of poly(AA‐b‐DXL) showed pH sensitivity, and both the copolymer networks of poly(AM‐b‐DXL) and poly(NIPAM‐b‐DXL) showed temperature sensitivity. Moreover, because of the low ceiling temperature of polyDXL, the networks containing polyacetal segments (PDXL) can degrade by treatment with a trace of appropriate cationic initiator. The polymer networks prepared were characterized by Fourier transform infrared, differential scanning calorimetry, and swelling data. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 3002–3006, 2002; DOI 10.1002/app.2329     

Synthesis of exfoliated PP/LDH nanocomposites via melt‐intercalation: Structure,thermal properties,and photo‐oxidative behavior in comparison with PP/MMT nanocomposites

Exfoliated polypropylene (PP)/layered double hydroxide (LDH) nanocomposites have been successfully synthesized via melt‐intercalation. Their structure, thermal properties, and photo‐oxidative behavior have been characterized by X‐ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), dynamic mechanical thermal analysis (DMA), X‐ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) spectrum. TGA and DMA data show that the PP/LDH nanocomposites have enhanced thermal stability compared with virgin PP and corresponding PP/montmorillonites (MMT) nanocomposites, especially in high temperature range during the thermal decomposition of the samples. XPS and FTIR results give positive evidence that the photo‐oxidation mechanism of PP in the PP/LDH materials is not modified compared with that of virgin PP. However, photo‐oxidation rate of PP/LDH materials is much lower than that of PP and PP/MMT samples, indicating that the PP/LDH nanocomposites have better UV‐stability. POLYM. ENG. SCI. 46:1153–1159, 2006. © 2006 Society of Plastics Engineers     

Data-based adaptive online prediction model for plant-wide production indices

A data-based adaptive online prediction model is proposed for plant-wide production indices based on support vector regression, a general method which we customized specifically to model very large data sets that are generated dynamically and periodically. The proposed model can update its parameters online according to the statistical properties of the training samples. Further, in order to improve the prediction precision, each sample is weighted with a dynamic penalty factor that considers the effect of each sample on the prediction model accuracy. Moreover, a customized procedure is introduced to handle large training sets. After having been convincingly evaluated on benchmark data, effectiveness and performance of our approach for plant-wide production indices is demonstrated using industrial data from an operating ore dressing plant over a range of scale in training data set size. The higher accuracy and shorter computation times than existing methods suggest that it may prove advantageous in actual application to dynamic production processes.     

Safe Landing Analysis of a Quadrotor Aircraft With Two Legs

We proposed a multi-propeller multifunction aerial robot (MMAR) that is composed of a quadrotor with two legs. The legs can increase the function of the robot. We found that the legs can increase the safety region of the robot during the landing. To study the safety problem, the dynamics of MMAR interacting with environment should be solved. On the basis of the interaction dynamics, this paper investigates the velocity constraint for safe landing of MMAR. The investigation begins from the kinematics and dynamics of MMAR in flight mode. Then the impact dynamics of MMAR during landing is developed. Furthermore, the landing safety problem is formulated by a series of constraint equations which can give a safety region of the velocity during landing. The safety region can give the safe velocity of the aerial robot before landing. Finally, simulation examples are presented using the proposed methodology. In the examples, a detailed safety region of a simulated MMAR is constructed and shown.     

A novel self-adaptive extreme learning machine based on affinity propagation for radial basis function neural network

In this paper, a novel self-adaptive extreme learning machine (ELM) based on affinity propagation (AP) is proposed to optimize the radial basis function neural network (RBFNN). As is well known, the parameters of original ELM which developed by G.-B. Huang are randomly determined. However, that cannot objectively obtain a set of optimal parameters of RBFNN trained by ELM algorithm for different realistic datasets. The AP algorithm can automatically produce a set of clustering centers for the different datasets. According to the results of AP, we can, respectively, get the cluster number and the radius value of each cluster. In that case, the above cluster number and radius value can be used to initialize the number and widths of hidden layer neurons in RBFNN and that is also the parameters of coefficient matrix H of ELM. This may successfully avoid the subjectivity prior knowledge and randomness of training RBFNN. Experimental results show that the method proposed in this thesis has a more powerful generalization capability than conventional ELM for an RBFNN.