Effects of NCO/OH molar ratio on miscibility and properties of semiinterpenetrating polymer networks from polyurethane and benzyl konjac glucomannan

Semi‐interpenetrating polymer network (semi‐IPN) films with different NCO/OH molar ratios of the urethane prepolymer, coded as UB, were prepared from polyurethane (PU) and benzyl konjac glucomannan (B‐KGM) by a casting method. The effect of the NCO/OH molar ratio of the urethane prepolymer on the miscibility and properties of the UB films was investigated using Fourier transform infrared spectroscopy, differential scanning calorimetry, dynamic mechanical thermal analysis, thermogravimetric analysis, and swelling and tensile tests. The results indicated that, with an increase of the NCO/OH ratio, the crosslink density of the UB films increased, resulting in improved miscibility between PU and B‐KGM and a relatively high light transmittance of the UB films. However, the thermal stability of the UB films decreased with increase of the NCO/OH ratio of the urethane prepolymer, due to the depolymerization of the urethane bonds of the PU networks. When the NCO/OH ratio increased from 2 to 4, the tensile strength of the UB films increased from 15 to 27 MPa, while the breaking elongation decreased from 72 to 16%, resulting from the chemical and physical crosslinks, namely, the enhancement of the covalent bonds and hydrogen‐bonding networks. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1304–1310, 2003     

高校自动排课系统算法比较分析

课程表的编排是高校教务管理中最为重要和复杂的一项工作。通过对几种自动排课算法的合理比较。统筹分析出各自的优劣,得出贪婪算法的综合适用性是最优的结论。在此基础之上．进一步分析贪婪算法是如何逐步解决排课的现实问题,并给出基于贪婪算法的自动排课系统算法的具体实现过程。     

氧空位对氧化锆相结构稳定性及相变过程的影响

从晶体学和配位学的角度，结合电化学技术，讨论了氧空位对氧化锆相结构结构稳定性的影响及氧化锆四方相单斜相转变过程中的作用。结果表明：氧空位的存在与变化不仅影响着氧化锆相结构的稳定性，而且影响着氧化锆的低温相变过程。对于含有一定担氧空位的亚稳四方相氧化锆，氧空位浓度的增加与减少都会进一步降低其结构稳定性，使之更加容晚地向单斜相转变     

Preparation and characterization of carboxymethyl konjac glucomannan/sodium montmorillonite hybrid films

Carboxymethyl konjac glucomannan (CKGM)/ sodium montmorillonite (MMT) hybrid films of various compositions were prepared by casting from a polymer/silicate water suspension. The structure and properties of the hybrid films were investigated by wide angle X‐ray diffraction (WAXD), transmission electron microscopy (TEM), attenuated total reflection infrared spectroscopy (ATR‐IR), differential scanning calorimetry (DSC), and tensile tests. The results from WXRD and TEM indicated that an intercalated CKGM/MMT nanocomposite film was obtained by polymer solution intercalation. WXRD and DSC showed that the high‐T_m crystal phase was induced by the presence of lower MMT loading, but the T_m of the hybrid films became weak with the increase of MMT content due to the polymer confinement. The hybrid films showed higher thermal stability and mechanical properties than that of the neat polysaccharide due to the strong interaction between hydroxyl and carbonyl group of CKGM and the silicate layer of MMT. Furthermore, the degree of swelling of the hybrid films was investigated in acidic buffer solutions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2954–2961, 2007     

橡胶冷喂料挤出机螺杆参数与机头压力实用数学模型的研究

运用正交回归试验方法，在Φ橡胶冷喂料挤出机实验台上，研究了螺杆主要参数（长径比，螺旋角，螺槽深度，螺杆几何压缩比）及主要挤出工艺、物性参数（螺杆转速、机头口型，胶料种类）对橡胶冷喂料挤出机机头压力的影响。对各实验因素及实验结果做了统计分析，确定了上述各因素对冷喂挤出机机头压力影响的显著因素，得出了机头压力与螺杆及工艺、物性参数之间的定量计算数学模型。     

节水型洗衣粉的研制

本文论述研制节水型洗衣粉的必要性及其制造过程。并对洗衣粉的表面活性剂、助剂、消泡剂进行配方优选，研制出去污力强的节水型洗衣粉。     

气升式内环流反应器中油滴的分散特性

本文研究了气升式内环流反应器中油滴的分散特性。以对数正态分布密度函数为油滴尺寸的分散模型,导出了油滴的Sauter平均直径解析式。对模型作了实验验证,关联了模型参数。提出了油滴的尺寸分布密度函数和Sauter平均直径的半经验式。结果表明计算值与实验值吻合良好。     

Multi-channel power allocation based on market competitive equilibrium in cognitive radio networks

Cognitive radios such as intelligent phones and Bluetooth devices have been considered essential goods in next-generation communication systems.Such devices will have to share the same frequency band owing to the limited bandwidth resource.To improve spectrum efciency,we formulate multi-channel power allocation as a market competitive equilibrium(CE)problem,and prove that its solution exists and is unique under the condition of weak interference.We then propose two distributed power allocation algorithms achieving CE,namely the fast convergent power allocation algorithm(FCPAA)and the social-fairness-aware FCPAA(SFAF).Theoretical analysis and simulation results demonstrate that the proposed algorithms lead to better system performance in terms of the guaranteed interference temperature constraint using the price mechanism instead of a strategy based on the Nash equilibrium.Moreover,it is shown that the FCPAA maximizes total utility,and converges more quickly than the method addressed in prior research with the help of improved round-robin rules.However,the FCPAA cannot ensure the same social fairness among secondary users as the SFAF scheme in both the non-fading channel and Rayleigh fading channel;the SFAF balances the individual utility by adjusting each user’s budget at the expense of a small quantity of system total throughput.     

PLC系统信号干扰与防范措施

结合现场,分析PLC控制系统中信号产生干扰的原因,和可能引起模板故障的因素,并提出相应解决方法.