Effects of preparation parameters on growth and properties of β-Ga2O3 film

The Ga$_{2}$O$_{3}$ films are deposited on the Si and quartz substrates by magnetron sputtering, and annealing. The effects of preparation parameters (such as argon-oxygen flow ratio, sputtering power, sputtering time and annealing temperature) on the growth and properties ($e.g.$, surface morphology, crystal structure, optical and electrical properties of the films) are studied by x-ray diffractometer (XRD), scanning electron microscope (SEM), and ultraviolet-visible spectrophotometer (UV-Vis). The results show that the thickness, crystallization quality and surface roughness of the $\beta $-Ga$_{2}$O$_{3}$ film are influenced by those parameters. All $\beta $-Ga$_{2}$O$_{3 }$films show good optical properties. Moreover, the value of bandgap increases with the enlarge of the percentage of oxygen increasing, and decreases with the increase of sputtering power and annealing temperature, indicating that the bandgap is related to the quality of the film and affected by the number of oxygen vacancy defects. The $I$-$V$ curves show that the Ohmic behavior between metal and $\beta $-Ga$_{2}$O$_{3}$ films is obtained at 900 ${^\circ}$C. Those results will be helpful for the further research of $\beta $-Ga$_{2}$O$_{3}$ photoelectric semiconductor.     

Fe_3O_4纳米粒子与慢病毒载体共同感染内皮祖细胞的促血管新生和MRI示踪的应用

采用化学共沉淀法制备了柠檬酸钠修饰Fe_3O_4纳米粒子(NPs),使用胎牛血清(FBS)改善Fe_3O_4NPs的分散性.实验表明Fe_3O_4NPs尺寸均匀,且具有良好的稳定性,FBS浓度小于5%(体积分数)时,Fe_3O_4NPs无聚集沉淀;在300 K下,饱和磁化强度达到74.86×10~(-3)A·m~2/g(74.86 emu/g);核磁共振T2序列成像时,75μg/m L Fe_3O_4NPs与慢病毒载体(LV)共同标记内皮祖细胞(EPCs)成像效果良好;而且EPCs具有稳定过表达目的基因血管内皮生长因子(VEGF)的能力.利用Fe_3O_4NPs与LV共同感染EPCs,可有效促进大鼠血管生成.说明修饰后的EPCs兼具核磁共振成像(MRI)示踪和促血管生成双重功能.     

CaCO3/PEEK复合体系的力学行为和热行为研究

以聚醚醚酮和碳酸钙复合体系为研究对象,考察了偶联剂和填料添加量对复合材料力学行为和热行为的影响.发现磺化聚醚醚酮作为偶联剂能有效地改善材料的力学性能,提高基体树脂的玻璃化转变温度,降低基体树脂的熔点,有助于改善聚醚醚酮的加工条件     

PEO-12-钨磷酸质子导电聚合物电解质膜

以聚氧乙烯(PEO)为基质, 在其中掺杂适量的钨磷酸, 制备PEO-H₃PW₁₂O₄₀质子导电聚合物电解质膜. XRD及IR测试表明体系中Keggin阴离子与PEO链相互作用形成新的化合物; Keggin阴离子的存在有利于水合质子的形成. PEO-H₃PW₁₂O₄₀复合膜的电导率室温最高可达4.0×10^－3 S•cm^－1.     

PEO-12-钨磷酸质子导电聚合物电解质膜

以聚氧乙烯(PEO)为基质, 在其中掺杂适量的钨磷酸, 制备PEO-H₃PW₁₂O₄₀质子导电聚合物电解质膜. XRD及IR测试表明体系中Keggin阴离子与PEO链相互作用形成新的化合物; Keggin阴离子的存在有利于水合质子的形成. PEO-H₃PW₁₂O₄₀复合膜的电导率室温最高可达4.0×10^－3 S•cm^－1.     

A comparison of different entransy flow definitions and entropy generation in thermal radiation optimization

In thermal radiation, taking heat flow as an extensive quantity and defining the potential as temperature T or the black body emissive power U will lead to two different definitions of radiation entransy flow and the corresponding principles for thermal radiation optimization. The two definitions of radiation entransy flow and the corresponding optimization prin ciples are compared in this paper. When the total heat flow is given, the optimization objectives of the extremum entransy dissipation principles （EEDPs） developed based on potentials T and U correspond to the minimum equivalent temperature difference and the minimum equivalent blackbody emissive power difference respectively. The physical meaning of the definition based on potential U is clearer than that based on potential T, but the latter one can be used for the coupled heat transfer optimization problem while the former one cannot. The extremum entropy generation principle （EEGP） for thermal radiation is also derived, which includes the minimum entropy generation principle for thermal radiation. When the radiation heat flow is prescribed, the EEGP reveals that the minimum entropy generation leads to the minimum equivalent thermodynamic potential difference, which is not the expected objective in heat transfer. Therefore, the minimum entropy generation is not always appropriate for thermal radiation optimization. Finally, three thermal radiation optimization examples are discussed, and the results show that the difference in optimization objective between the EEDPs and the EEGP leads to the difference between the optimization results. The EEDP based on potential T is more useful in practical application since its optimization objective is usually consistent with the expected one.     

超细高分散碳酸钙的原位制备及性能

利用油酸原位表面改性方法制备了一种高分散疏水碳酸钙纳米粒子.在低温碳化条件下,制备的超细碳酸钙纳米粒子的粒径可控制在40~50 nm之间.原位表面改性作用下油酸分子被接枝到超细碳酸钙纳米粒子的表面,使其分散性明显提高;此种超细填料的表面接触角为125.96°,由亲水性转变为疏水性.将质量分数为1%的超细碳酸钙纳米粒子填料添加到ABS树脂基体中,其白度值从62.47升高至87.96,可见该超细填料可以广泛应用到"白色家电"ABS专用树脂中.     

改进PID算法在浆液PH值控制系统中的应用

为了对浆液pH值控制系统进行全面的优化控制,使整个系统在最佳状态下运行,提出了一种改进PID算法。该算法利用单神经元具有自适应、自学习能力的优势,将神经元加入到PID算法中后,改进了控制系统稳定性和控制性能较差的问题;并结合浆液pH值控制系统的特点,设计了算法的具体流程。最后,利用改进前后的两种算法对优化问题进行了仿真分析,结果表明单神经元自适应PID算法具有更好的优化效果。     

发动机冷却系统仿真模拟及节温器的影响分析

本文基于MATLAB/Simulink仿真平台,建立了某型柴油活塞发动机冷却系统的一维仿真模型,研究了冷却系统对环境温度、气缸散热量等参数的敏感性,并分析了节温器对冷却系统敏感性及冷启动过程中动态特性的影响.结果表明,节温器对流量的分配和调节作用可以有效地增强系统对外部扰动的适应能力,使系统的工作更加稳定;对冷却系统参数的敏感性分析,可用于研究系统的工作特性,为系统的设计和运行控制提供依据;节温器的时间常数对冷却系统的动态特性影响显著,较小的时间常数有利于保证发动机的稳定工作.     

PEO-12-钨磷酸掺杂的质子导电聚合物电解质膜

以聚氧乙烯(PEO)为基质,在其中掺杂适量的钨磷酸,制备PEO-H3PW12O40质子导电聚合物电解质膜.XRD及IR测试表明体系中Keggin阴离子与PEO链相互作用形成新的化合物;Keggin阴离子的存在有利于水合质子的形成.PEO-H3PW12O40复合膜的电导率室温最高可达4.0×10-3S·cm-1.