Design of disturbance observer based on adaptive-neural control for large-scale time-delay systems in the presence of actuator fault and unknown dead zone

This article presents an adaptive neural compensation scheme for a class of large-scale time delay nonlinear systems in the presence of unknown dead zone, external disturbances, and actuator faults. In this article, the quadratic Lyapunov–Krasovskii functionals are introduced to tackle the system delays. The unknown functions of the system are estimated by using radial basis function neural networks. Furthermore, a disturbance observer is developed to approximate the external disturbances. The proposed adaptive neural compensation control method is constructed by utilizing a backstepping technique. The boundedness of all the closed-loop signals is guaranteed via Lyapunov analysis and the tracking errors are proved to converge to a small neighborhood of the origin. Simulation results are provided to illustrate the effectiveness of the proposed control approach.     

Production of hydrogen from methanol steam reforming using CuPd/ZrO2 catalysts – Influence of the catalytic surface on methanol conversion and CO selectivity

Electricity generation for mobile applications by proton exchange membrane fuel cells (PEMFCs) is typically hindered by the low volumetric energy density of hydrogen. Nevertheless, nearly pure hydrogen can be generated in-situ from methanol steam reforming (MSR), with Cu-based catalysts being the most common MSR catalysts. Cu-based catalysts display high catalytic performance, even at low temperatures (ca. 250 °C), but are easily deactivated. On the other hand, Pd-based catalysts are very stable but show poor MSR selectivity, producing high concentrations of CO as by-product. This work studies bimetallic catalysts where Cu was added as a promoter to increase MSR selectivity of Pd. Specifically, the surface composition was tuned by different sequences of Cu and Pd impregnation on a monoclinic ZrO₂ support. Both methanol conversion and MSR selectivity were higher for the catalyst with a CuPd-rich surface compared to the catalyst with a Pd-rich surface. Characterization analysis indicate that the higher MSR selectivity results from a strong interaction between the two metals when Pd is impregnated first (likely an alloy). This sequence also resulted in better metallic dispersion on the support, leading to higher methanol conversion. A H₂ production rate of 86.3 mmol h^?1 g^?1 was achieved at low temperature (220 °C) for the best performing catalyst.     

Electrolyte flow optimization and performance metrics analysis of vanadium redox flow battery for large-scale stationary energy storage

Vanadium redox flow battery (VRFB) is the best choice for large-scale stationary energy storage, but its low energy density affects its overall performance and restricts its development. In order to improve the performance of VRFB, a new type of spiral flow field is proposed, and a multi-physics coupling model and performance metrics evaluation system are established to explore the electrolyte distribution characteristics. The results show that the new spiral flow field can effectively improve the uniformity of electrolyte flow and alleviate the phenomenon of local concentration polarization as compared with the traditional serpentine flow field and parallel flow field. Due to the long flow channel and large pressure drop, the system efficiency is low. However, coulombic efficiency, voltage efficiency and energy efficiency are significantly better than the traditional flow fields. Therefore, the novel flow field has obvious advantages in the application of small stacks.     

刨花板工艺技术与其进步——刨花分选

从刨花板生产的刨花筛选与风选相关技术、工艺设计及生产过程工艺控制等方面,阐述了适应刨花分选工艺技术的相关影响因素与技术改进方案。     

高压压气机转子结构设计及改进方法

为提高设计效率并快速得到适于工程应用的高压压气机转子结构，以改型设计方法为基础对某高压压气机转子结构进行了详细设计，同时对结构改进方法进行了一定的探索。采用叶—盘耦合系统循环对称结构算法及整体转子系统二维轴对称结构算法进行强度设计及改进，前轴颈最大应力下降最多达26%；其次进行支承结构设计，计算校核母型机轴承承载能力。结果表明：轴向力安全裕度最小为28%，轴承寿命大于100 000 h；给出2种调整鼠笼厚度的估算方法用以指导三维有限元计算，同时计算得到前支承刚度；通过二维有限元分析模型计算转子的临界转速，仅将后轴承支承位置沿压气机轴线向后移动7.5 mm，全运行工况转速与第2阶临界转速的安全裕度由18.5%提高到21.2%。     

Design and synthesis of side-chain optimized poly(2,6-dimethyl-1,4-phenylene oxide)-g-poly(styrene sulfonic acid) as proton exchange membrane for fuel cell applications: Balancing the water-resistance and the sulfonation degree

Side-chain optimized poly (2,6-dimethyl-1,4-phenylene oxide)-g-poly (styrene sulfonic acid) (PPO-g-PSSA) is designed with balanced water-resistance and sulfonation degree. The PPO-g-PSSA is synthesized by controlled atom-transfer radical polymerization (ATRP) from brominated poly (2,6-dimethyl-1,4-phenylene oxide) (PPO-xBr) and ethyl styrene-4-sulfonate and followed by hydrolysis. A series of PPO-g-PSSA are prepared possessing different bromination degree (x) of PPO-xBr and polymerization degree (m) of the side-chains and the water-resistances of the fabricated membranes are investigated. The results show that a PPO-g-PSSA at relatively low x (x < 0.2) and high m (m > 4) exhibits good balance between the water-resistance and the sulfonation degree. Namely, it displays suitable proton conductivity with compromised water-resistance. Moreover, a maximum ion exchange capacity (IEC) of 3.24 mmol g^?1 is reached without the sacrifice of water-resistance. In addition, PPO-g-0.08PSSA-13 and PPO-g-0.14PSSA-4 are chosen characterized by thermogravimetric analysis, proton conductivities and mechanical properties. At 90% RH, the optimized PPO-g-0.08PPSA-13 possesses a proton conductivity of 37.9 mS cm^?1 at 40 °C and 45.5 mS cm^?1 at 95 °C, respectively.     

Design and computational analysis of a metal hydride hydrogen storage system with hexagonal honeycomb based heat transfer enhancements-part A

In this study, design and performance analysis is carried out for a 10 kWh metal hydride based hydrogen storage system. The system is equipped with distinctive aluminium hexagonal honeycomb based heat transfer enhancements (HTE) having higher surface area to volume ratio for effective heat transfer combined with low system weight addition. The system performance was studied under different operating conditions. The optimum absorption condition was achieved at 35 bar with water at room temperature as heat transfer fluid where up to 90% absorption was completed in 7200 s. The performance of the reactor was observed to significantly improve upon the addition of the HTE network at a minimal system weight penalty.     

Wholesale electricity spot market design: Find a way or make it

Designing wholesale electricity spot markets even after three decades of experience in dozens of countries continues to be a challenging task. The challenges arise from a myriad of options that exist without adequate level of unbiased guidance, and experiences in real-life markets where successes and failures are also open to the interpretation of experts. This is particularly a critical issue in the developing world where wholesale spot markets are yet to be established in 80 % of the countries and the experience in the remaining 20 % countries with an operational market, is mixed. There are certain trends in selection of market design that leave significant room for improvement including fallacies that should be avoided. Implementation of markets have also been problematic in most cases including unrealistic timetable and inadequate consideration of transition mechanism that have also hampered market development. In this article, we present our views on how policy makers, stakeholders and development institutions should think about the choices around market design and some of the common pitfalls around its implementation.     

Effects of air purification of indoor PM2.5 on the cardiorespiratory biomarkers in young healthy adults

Ambient fine particulate matter (PM_2.5), as one of the predominant air pollutants, has achieved effective control in recent years in China. Whether the use of indoor air purifiers is still necessary needs further exploration. A randomized crossover trial was conducted in 54 healthy students in Beijing, China. Participants were randomized assigned to the use of real or sham high-efficiency particulate air filter (HEPA) for a week and changed the status after a washout period. Health measurements of cardiorespiratory biomarkers were performed at the end of each period. Linear mixed-effects models were used to evaluate the association between PM_2.5 exposure and cardiorespiratory biomarkers. Compared with sham air purification, average diastolic blood pressure (DBP), fractional exhaled nitric oxide (FeNO), and 8-isoprostane (8-isoPGF2α) levels decreased significantly in the real purification. The effects of indoor air purification on lung function indicators including forced expiratory volume in one second (FEV₁), peak expiratory flow (PEF), and forced expiratory flow between the 25th and 75th percentile of forced vital capacity (FEF_25%–75%) were also significant. Our findings showed a protective effect of indoor HEPA air purifiers on cardiorespiratory health of young healthy adults reflected by the decreased blood pressure, respiratory inflammation, and systematic oxidative stress and improved lung function.     

Design and eco-innovation: micro-evidence from the Eurobarometer survey

ABSTRACT

This paper investigates the role of design in making firms eco-innovate. Going beyond the ‘packed’ approach of environmental studies about ‘eco-design’, we maintain that the eco-innovative impact of design is correlated with the firm’s decision to invest in it. In turn, design investment is assumed connected with the use firms make of design. By pooling the Eurobarometer 2015 and 2016 surveys, we test for these arguments with respect to a sample of nearly 4500 European and non-European (US and Switzerland) manufacturing firms. Results confirm that the firms’ capacity of eco-innovating increases when they invest in design, also by making this investment dependent on the role of design within the firm. The relationship between eco-innovation and design appears robust with respect to the different kinds of ‘eco-innovators’ that the Eurobarometer enables us to consider, while some interesting variability emerges when splitting the sample by group of countries and industries.