基于排列熵和支持向量机的癫痫发作预测研究

针对癫痫发作给病人带来的巨大伤害,为临床治疗留下足够空余时间,提出一个可以预测癫痫发作的系统模型。对21名癫痫病人进行研究,提取具有较低算法复杂度的排列熵构成特征向量,将其输入支持向量机（support vector machine,SVM）训练出学习模型,用来识别发作期样本,利用投票机制充分考虑病人差异来判断所处状态,最终实现癫痫的实时预测。结果表明,其中81%的发作可以提前平均50多分钟预测到,且具有较低的误报率。为癫痫发作预测系统的理论研究打下坚实基础。     

PbNb2O6基压电陶瓷的高温介电性能研究

本文在PbNb2O6基础上采用Ba^2＋取代Pb^2＋离子,并通过添加Cr2O3、Y2O3、Sm2O3、Nd2O3和CeO2等氧化物进行掺杂改性,研究不同掺杂剂对PbNb2O6陶瓷材料结构的影响,寻找提高压电性能及居里温度的途径.试验结果表明,掺杂后的偏铌酸铅显微结构发生了变化,适量的掺杂可获得压电性能和工艺稳定性能很好,且居里温度较高（420℃～600℃）的改性PbNb2O6系压电陶瓷,可分别满足350℃和500℃以上高温应用环境的要求.     

Nickel foam and carbon felt applications for sodium polysulfide/bromine redox flow battery electrodes

The first use of nickel foam (NF) as electrocatalytic negative electrode in a polysulfide/bromine battery (PSB) is described. The performance of a PSB employing NF and polyacrylonitrile (PAN)-based carbon felt (CF) as negative and positive electrode materials, respectively, was evaluated by constant current charge-discharge tests in a single cell. Charge/discharge curves of the cell, positive and negative electrodes show that the rapid fall in cell voltage is due to the drop of positive potential caused by depletion of Br₂ dissolved in the catholyte at the end of discharge. Cell voltage efficiency was limited by the relatively high internal ohmic resistance drop (iR drop). Polarization curves indicated that both NF and CF have excellent catalytic activity for the positive and negative redox reactions of PSB. The average energy efficiency of the single cell designed in this work could be as high as 77.2% at 40 mA cm⁻² during 48 charge-discharge cycles.     

Synthesis of polystyrene end-capped with pyrene via reversible addition-fragmentation chain transfer polymerization

A novel benzodithioate compound with a pyrene structure in the R group, pyrenylmethyl benzodithioate (PMB) was synthesized. Using PMB as the chain transfer agent (CTA), the RAFT polymerizations of styrene with AIBN as an initiator were carried out in different reaction conditions. The results indicated that PMB was an effective CTA for the RAFT polymerizations of styrene with the “living”/controlled characteristics. The structures of the obtained polymers were characterized by ¹H NMR. The results showed that majority of the polymer chains contained the pyrene moiety in the chain end. The enhanced fluorescence property in CHCl₃ solution was observed. The chain-extension experiments of the obtained polystyrene (PS) with the monomers of styrene and methyl acrylate were successfully carried out.     

A203型低温氨合成催化剂使用小结

对Ａ２０３型低温氨合成催化剂的使用进行总结，介绍了该催化剂的装填，升温还原情况及使用效果。     

J-R curve calculation with the normalization method for toughened polymers

The method of normalization is used to develop the J-R curve fracture toughness characterization for polymeric materials. This method can develop J-R curves directly from load vs. displacement records without a need for an on-line crack monitoring system. It was used previously to develop J-R curves for metallic materials and is applied here for the first time to polymer materials. Single edge notched bend specimens of rubber toughened nylon 6/6 and rubber toughened amorphous nylon are used in this study. The J-R curves from the method of normalization are compared with the results obtained from the multiple specimen method of ASTM Standard E813. The results show that the method of normalization gives reasonable J-R curves; both methods show agreement over the early J-R curve region. In addition the J_Ic values are determined for each method and compared. Based on this work it is suggested that the method of normalization could be used as a general test method to develop J-R curves for polymeric materials.     

Interlayer delamination and adhesion of coextruded films

Efforts to evaluate interlayer adhesion of coextruded films are often hampered by the inability to initiate delamination. On the other hand, interlayer delamination was often noticed at cut or trimmed edges of coextruded films. In this study, a test method was developed by first initiating delamination by uniaxial stretching and then measuring interlayer adhesion by peel test. Delamination was initiated by uniaxial stretching under controlled conditions for samples with double‐neck geometry. The double‐neck geometry was designed to create a specimen for the subsequent 180° peel test. Peel force was used to quantify interlayer adhesion of coextruded films based on polycarbonate and its copolymers. With this two‐step technique, coextruded films with peel force as high as 5300 N/m or 30 lb./in. were quantified. In addition, effects of copolymer composition and coextrusion processing condition on interlayer adhesion of these coextruded films were clearly demonstrated. A great deal of variation of interlayer adhesion across film surface was also revealed. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3901–3909, 2004     

二苯二硒的合成和晶体结构

报道了一种新的合成工艺,采用氯化镉为催化剂,利用空气中的氧气直接氧化苯硒酚合成了二苯二硒晶体,表征了其晶体结构和红外光谱性质。晶体属于正交晶系,空间群 P21 21 21,a= 0 5646 (2) nm,b= 0 8288 (3) nm,c=2 4100(9)nm; V=1 1276(7)nm3,Dc=1 839 g·cm-3,Z=4, R=0 0259。     

吸湿介质对碳纤维增强铸型尼龙复合材料的吸湿行为及力学性能的影响

本文对碳纤维增强铸型尼龙(CF／MC 尼龙)复合材料在不同吸湿介质中的吸湿行为进行了研究。结果表明，对于纤维体积分数为10％的碳纤维增强铸型尼龙复合材料(10％CF／MC尼龙复合材料)，随着吸湿介质的PH值减小，它的吸湿率增大。同时，经过吸湿后，10％CF／MC尼龙复合材料的弯曲强度有明显的下降。随着吸湿介质的PH值减小，试样的弯曲强度下降。使用环境扫描电子显微镜观察在10％HCl溶液中吸湿的试样的剪切断口形貌，得到的结果与吸湿实验的结果一致。     

Electrochemical capacitance of well-coated single-walled carbon nanotube with polyaniline composites

Well-coated single-walled carbon nanotube (SWNT) with polyaniline (PANI) composite electrodes with good uniformity for electrochemical capacitors are prepared by the polymerization of aniline containing well-dissolved SWNTs. The capacitance properties are investigated with cyclic voltammetry, charge-discharge tests and ac impedance spectroscopy. The composite electrode shows much higher specific capacitance, better power characteristics and is more promising for application in capacitor than pure PANI electrode. The effect and role of SWNT in the composite electrode are also discussed in detail.