面向聚类的平面反射数据扰动方法

面向聚类的数据隐藏通常使用数据扰动技术防止敏感信息泄露。针对现有的面向聚类的数据扰动方法隐私保护度低的问题,提出一种基于平面反射的数据扰动方法,将发布对象的全部属性两两配对构成平面上的点,再随机选择一条直线,作每对属性关于直线的对称点,转换后的数据即为发布的数据。实验结果表明,这种方法具有较好的隐私保护度和聚类可用性,且对高维数据有良好的适应性。     

Synthesis and characterization of new functional poly(urethane‐imide) crosslinked networks

To synthesize new functional poly(urethane‐imide) crosslinked networks, soluble polyimide from 2,2′‐bis(3,4‐dicarboxyphenyl) hexafluoropropane dianhydride, 4,4′‐oxydianiline, and maleic anhydride and polyurethane prepolymer from polycaprolactone diol, tolylene 2,4‐diisocyanate and hydroxyl ethyl acrylate were prepared. Poly(urethane‐imide) thin films were finally prepared by the reaction between maleimide end‐capped soluble polyimide (PI) and acrylate end‐capped polyurethane (PU). The effect of polyurethane content on dielectric constant, residual stress, morphology, thermal property, and mechanical property was studied by FTIR, prism coupler, Thin Film Stress Analyzer (TFSA), XRD, TGA, DMTA, and Nano‐indentation. Dielectric constant of poly(urethane‐imide) thin films (2.39–2.45) was lower than that of pure polyimide (2.46). Especially, poly(urethane‐imide) thin films with 50% of PU showed lower dielectric constant than other poly(urethane‐imide) thin films did. Lower residual stress and slope in cooling curve were achieved in higher PU content. Compared to typical polyurethane, poly(urethane‐imide) thin films exhibited better thermal stability due to the presence of the imide groups. The glass transition temperature, modulus, and hardness decreased with increase in the flexible PU content even though elongation and thermal expansion coefficient increased. Finally, poly(urethane‐imide) thin films with low residual stress and dielectric constant, which are strongly affected by the morphological structure, chain mobility, and modulus, can be suggested to apply for electronic devices by variation of PU. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 113–123, 2006     

Controlled coagulation of emulsion polymers

Coagulation of latex particles is most often carried out in the diffusion limited aggregation (DLA) regime where the time for coagulation to take place is on the millisecond timescale. This process produces aggregates of low density, irregular shape, and a broad particle size distributions. When the coagulation is carried out in the reaction limited aggregation (RLA) regime, a coagulation time of about 1–120 sec, the system can be controlled by mixing to yield dense, spheroidal aggregates with a very narrow particle size distribution. The important variables in the RLA process for butyl acrylate/methyl methacrylate (BA/MMA) latexes were found to be mixing intensity, latex copolymer composition, and coagulation temperature. Dried aggregates formed in the RLA process were found to have excellent powder flow properties and low dustiness.     

聚氨酯／聚苯乙烯互穿聚合物网络的结构与性能研究

通过改变组分比研究了PU/PS IPN结构与性能变化的规律。结果表明,在PU/PS为70/30时,电镜照片上呈现精细的细胞结构,相区尽寸缩小,网络间互穿程度最高,且溶胀度最低。热力学性能也同时出现最佳值,     

The effect of vacuum evaporation plating on phase structure and electrochemical properties of AB5–5 mass% LaMg3 composite alloy

In this paper, Cu, Al and Ni were plated on the AB₅–5 mass% LaMg₃ composite hydrogen storage alloy using a vacuum evaporation plating method. The phase structure and the electrochemical properties were investigated. The X-ray diffraction (XRD) analysis shows that the phase structure is not changed obviously after the plating Cu, Al and Ni on the composites. The electrochemical tests show that maximum discharge capacity, high rate dischargeability (HRD), dischargeability at low temperature and cyclic stability was improved by vacuum evaporation plating Cu, Al and Ni. Maximum of discharge capacity of the AB₅–5 mass% LaMg₃ composite alloy plating Ni can reach 351 mAh/g, which is 3.5% higher than that of the untreated. HRD at I_d = 1200 mA/g of the composite alloy plating Cu is 45.0% of that at 60 mA/g, which is 20.4% higher than the untreated. Discharge capacity of the composite alloy plating Cu at low temperature 233 K is 205 mAh/g, which is 57.3% of that at 298 K, and it is much higher than 36.8% of the untreated composites. The discharge capacity retention of the composite alloy plating Al after 200 cycles is 7.8% higher than the untreated.     

Catalytic characteristics of various rubber-reinforcing carbon blacks in decomposition of methane for hydrogen production

Carbon black has recently been reported to act as an effective catalyst for methane decomposition and to exhibit stable catalytic behavior despite carbon deposition, and thus it can be used for CO₂-free production of hydrogen from natural gas. In this work, various carbon blacks with different primary particle size were investigated with respect to methane decomposition under atmospheric pressure from 1123 to 1223 K. Catalytic characteristics, such as activity, activation energy and reaction order, were investigated and compared. It was observed that with decreasing primary particle size (or increasing specific surface area), the specific activity increased and the activation energy decreased. The reaction orders for various pelletized, rubber-reinforcing carbon blacks were 0.6–0.7, about the same regardless of the primary particle size, while they were near 1 for fluffy carbon blacks. Fluffy carbon black showed higher activity and activation energy than the pelletized carbon black of the same primary particle size. Changes of the surface morphology during carbon deposition were observed by TEM. Variations of the number of active sites were discussed in regard of the primary particle size, carbon deposition and binder. The presence of different types of active sites was also suggested.     

水热法制备纳米尖晶石型NiFe_2O_4及表征

分别采用水热法、共沉淀法合成了纳米尖晶石型铁氧体—NiFe2O4晶体,对两种方法所合成的样品进行了比较,分析了不同合成方法的优缺点,确定水热法为比较适宜的合成该类复合氧化物的方法,该法合成的NiFe2O4晶体的平均粒径仅为15.9nm,且粒度分布十分均匀。此外,通过对实验结果的测定与分析探讨了影响水热制备的几种可能的因素,确定了水热合成的适宜的沉淀剂为NaOH溶液,水热合成适宜的温度为200℃。     

聚合物多元醇产品质量的影响因素与控制

从内在和外在质量两个方面，简要论述了影响聚合物多元醇(POP)产品质量的因素和控制产品质量的措施。     

Oxidative stability of soybean oil fatty acid methyl esters by oil stability index (OSI)

Biodiesel, an alternative diesel fuel derived from transesterification of vegetable oils or animal fats, is composed of saturated and unsaturated long-chain FA alkyl esters. During long-term storage, oxidation caused by contact with air (autoxidation) presents a legitimate concern with respect to monitoring and maintaining fuel quality. Extensive oxidative degradation may compromise quality by adversely affecting kinematic viscosity, acid value, or PV. This work examines the oil stability index (OSI) as a parameter for monitoring the oxidative stability of soybean oil FAME (SME). SME samples from five separate sources and with varying storage and handling histories were analyzed for OSI at 60°C using an oxidative stability instrument. Results showed that OSI may be used to measure relative oxidative stability of SME samples as well as to differentiate between samples from different producers. Although addition of α-tocopherol or TBHQ increased OSI, responses to these antioxidants varied with respect to SME sample. Variations in response to added antioxidant were attributed to aging and other effects that may have caused oxidative degradation in samples prior to acquisition for this study. Results showed that OSI was more sensitive than iodine value in detecting the effects of oxidative degradation in its early stages when monitoring SME during storage.