基于RBF神经网络的发酵过程菌体浓度的软测量

针对微生物发酵过程中菌体细胞浓度难以实时在线检测的问题,从生物细胞代谢角度分析了发酵过程中生物代谢参数的相关性,找出了能够表示生物变量大小的代谢参数,然后将这些参数作为输入变量,建立了菌体细胞浓度软测量的R B F神经网络模型,为复杂系统中生物量参数的检测提供了一条有效途径。仿真结果表明,该软测量方法具有较高的精度,能很好地应用于生物发酵过程。     

Electro-oxidation of dimethyl ether on Pt/C and PtMe/C catalysts in sulfuric acid

The electro-oxidation of dimethyl ether (DME) on PtMe/Cs (Me = Ru, Sn, Mo, Cr, Ni, Co, and W) and Pt/C electro-catalysts were investigated in an aqueous half-cell, and compared to the methanol oxidation. The addition of a second metal enhanced the tolerance of Pt to the poisonous species during the DME oxidation reaction (DOR). The PtRu/C electro-catalyst showed the best electro-catalytic activity and the highest tolerance to the poisonous species in the low over-potential range (<0.55 V, 50 °C) among the binary electro-catalysts and the Pt/C, but at the higher potential (>ca. 0.55 V, 50 °C), the Pt/C behaved better than PtRu/C. The apparent activation energy for the DOR decreased in the order: PtRu/C (57 kJ mol⁻¹) > Pt₃Sn/C (48 kJ mol⁻¹) ≈ Pt/C (46 kJ mol⁻¹). On the other hand, the activation energy for the MOR showed a different turn, decreased in the following order: Pt/C (43 kJ mol⁻¹) > Pt₃Sn/C (35 kJ mol⁻¹) ≈ PtRu/C (34 kJ mol⁻¹). The temperature dependence of the DOR was greater than that of the oxidation of methanol (MOR) on the PtRu/C.     

Polyaniline as a Gas-Sensor Material

Polyaniline (PANI) was synthesized by oxidative polymerization of aniline using ammonium persulfate in an acid medium. The polyaniline salt was converted to base form by treatment with ammonium hydroxide. The polyaniline base was dissolved in N-methyl pyrrolidone (NMP) for film casting. The cast film was doped with HCl for obtaining higher conductivity. Both doped and undoped PANI films were characterized by UV-visible, FTIR, and XRD analyses. The electrical conductivity of the PANI film was studied by a four-point probe method at room temperature. Finally, ammonia gas-sensing characteristics of the prepared polyaniline film were studied by measuring the change in electrical conductivity on exposure to ammonia gas at different concentrations. The influence of concentration of acid during polymerization of aniline and dopant concentration on the gas sensing characteristics of PANI film are reported in this paper.     

Growth of La2Mo2O9 films on porous Al2O3 substrates by radio frequency magnetron sputtering

Synthesis conditions of La₂Mo₂O₉ thin film by radio frequency (RF) sputtering technique on Al₂O₃ ceramic substrates are studied. It is found that the deposition temperature and oxygen partial pressure are the most important factors for obtaining pure La₂Mo₂O₉ films. Varying both parameters, Mo-rich, stoichiometric, and Mo-deficient films are obtained. With increasing the La:Mo ratio, films become denser. A crust layer is observed on top of the Mo-rich and the Mo-deficient films. The formation of the La₂Mo₂O₉ phase is discussed with respect to the sputtering mechanism.     

户用PV系统设计

由于能源短缺和环境污染的问题日益严重,改善能源结构,保护环境,已成为我国在新世纪经济发展高速期所面临的重要课题。尤其是在居住建筑中,采用清洁、储量巨大、无地域限制和能源质量高等诸多优点的太阳能,成为近些年国内研究的热点,引起了各界的关注和重视,科研院所、相关企业等部门都在积极的探索和实践。本文介绍一种户用太阳能光伏发电系统(又称PV系统)的计算流程,仅供参考。     

双剪切梁式称重传感器滞后误差分析

双剪切梁式称重传感器(桥式称重传感器)在料斗、料仓、料罐吊车、地中衡、轨道衡等称重系统得到广泛利用.由于这种传感器的弹性体与底座之间采用螺栓联结,弹性体与底座以及弹性体与螺母之间的接触将对传感器的滞后特性产生重大影响.本文将通过有限单元建模的方法对双剪切梁式称重传感器的滞后特性进行研究.研究结果表明,弹性体的结构参数以及接触面的摩擦系数对传感器滞后有明显的影响.     

Ca2+对悬浮培养HEK293细胞的细胞团形成、细胞生长和代谢的影响

利用HEK293细胞在悬浮培养中具有聚集成团的体外培养特性,在250ml的Bellco的搅拌培养体系中,以细胞团粒径、细胞粒径、细胞数、细胞活力、葡萄糖比消耗速率 (qglc)、乳酸比生产速率 (qlac) 和乳酸对葡萄糖得率 (Ylac/glc) 为观察指标,考察了HEK293细胞在Ca2 浓度设置为0μmol/L、250μmol/L、500μmol/L、750μmol/L和1000μmol/L的搅拌培养体系中的细胞团形成、细胞生长和代谢.实验发现:培养基中的Ca2 浓度决定着HEK293细胞在悬浮培养中能否形成细胞团并影响着细胞团的粒径分布和细胞团内细胞相互连接的紧密程度;在250～1000μmol/L的Ca2 浓度范围内,HEK293细胞团的平均粒径与培养基中的Ca2 浓度成正比;Ca2 浓度对以细胞团的形式悬浮培养的HEK293细胞的生长和代谢无明显的影响.实验结果提示,Ca2 浓度是调节HEK293细胞团粒径分布、维持悬浮细胞团中HEK293细胞正常生长和代谢的有效控制参数.