直接甲醇燃料电池质子交换膜的发展现状

直接甲醇燃料电池(DMFC)是20世纪90年代兴起的第六代燃料电池,以其诸多的优点引起人们的广泛关注和研究。其中聚合物电解质膜是DMFC的关键技术,起着隔离阴阳极、质子传输、绝缘电子的作用。它的作用决定着DMFC的输出功率、电池效率、成本及应用前景。本文介绍了已商品化的全氟磺酸膜(Nafion膜)的结构及性能、以及替代膜的国内外发展现状,指出DMFC用膜的研究是21世纪能源研究的重点。     

中轻依兰二级计量系统Y2K问题的应急措施

介绍以修改系统日期来避免Ｙ２Ｋ问题时,如何在Ｅｘｃｅｌ工作表中自动输入真实日期的简单方法。     

适应敏捷制造的单元控制器体系结构

分析了敏捷制造生产模式下单元控制器的特点。运用面向对象的分析方法 ,对制造系统进行了抽象和概括 ,建立了单元控制器的功能模型和数据模型。提出了单元控制器的自适应递阶式控制结构 ,建立了基于 CORBA的单元控制器软件开发平台。该单元控制器体系结构模型 ,具有相对于具体应用过程的独立性 ,相对于制造环境的独立性 ,相对于计算机系统的独立性 ,以及良好的可重构性、鲁棒性和较强的对外通讯协调能力 ,满足敏捷制造对单元控制器的要求     

基于ATM的无源光网络的媒质接入控制(MAC)协议及其性能分析

结合以ＡＴＭ为基础的无源光网络的Ｇ．９８３建议,提出了一个基于预留的 接入控制协议,通过建模仿真,分析了此协议在多种业务流组合下的时延和时延变化性能,并提出了一种硬件实现方案。     

A cell evolution method for reliability-based design optimization

The reliability-based design optimization (RBDO) presents to be a systematic and powerful approach for process designs under uncertainties. The traditional double-loop methods for solving RBDO problems can be computationally inefficient because the inner reliability analysis loop has to be iteratively performed for each probabilistic constraint. To solve RBDOs in an alternative and more effective way, Deb et al. [1] proposed recently the use of evolutionary algorithms with an incorporated fastPMA. Since the imbedded fastPMA needs the gradient calculations and the initial guesses of the most probable points (MPPs), their proposed algorithm would encounter difficulties in dealing with non-differentiable constraints and the effectiveness could be degraded significantly as the initial guesses are far from the true MPPs. In this paper, a novel population-based evolutionary algorithm, named cell evolution method, is proposed to improve the computational efficiency and effectiveness of solving the RBDO problems. By using the proposed cell evolution method, a family of test cells is generated based on the target reliability index and with these reliability test cells the determination of the MPPs for probabilistic constraints becomes a simple parallel calculation task, without the needs of gradient calculations and any initial guesses. Having determined the MPPs, a modified real-coded genetic algorithm is applied to evolve these cells into a final one that satisfies all the constraints and has the best objective function value for the RBDO. Especially, the nucleus of the final cell contains the reliable solution to the RBDO problem. Illustrative examples are provided to demonstrate the effectiveness and applicability of the proposed cell evolution method in solving RBDOs. Simulation results reveal that the proposed cell evolution method outperforms comparative methods in both the computational efficiency and solution accuracy, especially for multi-modal RBDO problems.     

New evidence for a role of Bisphenol A in cell integrity. Implications in the human population

Bisphenol A (BPA) is a xenoestrogen known for its implications for the endocrine systems and several other organs, including the kidneys. Recent renal studies have shown that BPA can induce alterations of the cytoskeleton and cell adhesion mechanisms such as a podocytopathy with proteinuria and hypertension, alterations involved in the progression of renal diseases. These data and the fact that BPA is known to be present in the urine of almost the entire population strongly suggest the critical need to reevaluate BPA exposures considered safe.     

Resveratrol-related compounds: Potential for cancer and beyond

The nutraceutical resveratrol is associated with a range of biological effects, from antibiotic to anti-inflammatory activities. One major axis of research has sought to harness its anti-tumour potential, with promising preclinical results and early clinical trials. A second strong interest relies on the anti-ageing effects ascribed to the compound and its application to stem cell research. It is becoming clear however that these possible favourable effects are conditioned by a set concentration range not easily controllable in vivo. Here we evoke novel developments in the field that could lead to more reliable conditions for the translational use of resveratrol-based compounds.     

PEM fuel cell low flow FDI

In this work, a signal-based diagnostic methodology that can isolate PEM fuel cell low anode and cathode flow rates is introduced. The methodology is based on calculating symptoms of the faults, and comparing them versus thresholds that are calibrated a priori of real time operation. The novelty with the methodology is in using cell voltage oscillations, imposed by a small signal oscillation on the cathode output pressure, to isolate cathode flooding. Furthermore, it is shown in this work that the fixed reference cathode stoichiometry commonly used in the literature for isolating cathode starvation is not reliable and results in false alarms, and an adaptive scheme is proposed. It is also shown that a fixed stoichiometry scheme can be used to reliably isolate anode starvation. These measures are then used to design a signal-based diagnostic algorithm to isolate cathode flooding, cathode starvation, and anode starvation in real time. Finally, the robustness of the algorithm to changes in current, pressure, temperature, and humidity operating conditions is examined.     

Non-academic internet use in the classroom is negatively related to classroom learning regardless of intellectual ability

The use of laptops and cell phones in the classroom is increasing but there is little research assessing whether these devices create distraction that diminishes learning. Moreover, the contribution of intellectual ability to the relationship between learning and portable device use has not been thoroughly investigated. To bridge this gap, students in an introductory psychology class were surveyed about the frequency and duration of their use of various portable devices in the classroom. Internet use negatively predicted exam scores and added to the prediction of classroom learning, above a measure of intellectual ability. Furthermore, students discounted the effect of using portable devices on learning over time. Concomitantly, those with higher intellectual ability reported using the internet more in class over time. Thus, higher rates of internet use were associated with lower test grades and students' beliefs about this relationship did not reflect their ability to multi-task effectively.     

Scale-up studies for stable,long-term indoor and outdoor production of hydrogen by immobilized Rhodobacter capsulatus

Photofermentative hydrogen production by immobilized Rhodobacter capsulatus YO3 was carried out in a novel photobioreactor in sequential batch mode under indoor and outdoor conditions. Long-term H₂ production was realized in a 1.4 L photobioreactor for 64 days using Rhodobacter capsulatus YO3 immobilized with 4% (w/v) agar on 5 mM sucrose and 4 mM glutamate. The highest hydrogen yield (19 mol H₂/mol sucrose) and hydrogen productivity (0.73 mmol H₂ L^?1 h^?1) were achieved indoors on 5 mM sucrose. The effect of initial sucrose concentration (5 mM, 10 mM, and 20 mM) on hydrogen production was also investigated. Sustained hydrogen production was carried out under natural, outdoor conditions as well. For the outdoor experiments, the highest hydrogen productivity and yield were obtained as 0.87 ± 0.06 mmol H₂ L^?1 h^?1 and 6.1 ± 0.2 mol H₂/mol sucrose, respectively on 10 mM sucrose. Furthermore, this system prevented sudden pH drops and fluctuations caused by the utilization of sucrose throughout the process. These results demonstrate that a proper immobilization setup can lead to long-term efficient and robust hydrogen production even under naturally varying conditions.