Optimization of self-regulated hydrogen production from photovoltaic energy

The use of photovoltaic energy (PV) for the production of hydrogen by using autonomous modular self-regulated systems is studied. Results are compared with those obtained for controlled systems. It was proved that for small and low-cost applications, it is possible to eliminate any control system with yields as high as 91.2% in the PV-electrolyzer interface for a sunny day. Self-regulated systems are thus an excellent, safe, cheap and environmentally friendly alternative for applications in isolated sites, especially in emerging countries.     

基于法律政策和检测性质的市县级食药检测机构整合探讨

本研究通过国家认证认可监督管理委员会发布的《2016年度检验检测服务业统计报告》相关数据,基于食品药品法律政策、检测性质、规模效应、检测能力建设等方面,对基层食品药品类检验检测资源整合路径进行论证分析。面对当前事业单位机构改革,本研究提出市县级食品药品类检验检测机构应进行跨行业、跨部门、跨层级优化整合的建议,建立以政府实验室为基础、市场检测为补充的食品药品安全检验检测资源配置模式,为实现基层食品药品安全监管现代化治理提供良好的检验检测技术服务支撑能力。     

初始制动时预测湿式制动器热对流特性的积分方法

湿式制动器对重型车辆安全具有关键影响，以湿式制动器摩擦副间隙的冷却液压油（Automotive transmission fluid，ATF）为研究对象，考虑车辆初始制动阶段流体的黏性摩擦和层流流动特征，利用积分方法建立了摩擦副流体的非稳态能量方程，并获得了能同时满足轴向和径向边界条件的三维温度和热流密度显式解析表达式，通过简化动量方程和多项式分布假设也获得了径向速度和压力的理论解，与以往试验对比表明，压力和温度解析解与试验结果具有较好的一致性，理论模型有望推广用于液黏离合器等其他HVD装置的ATF速度场、温度场和热流密度场的理论预测。     

A multilevel sampled‐data approach for resilient navigation and control of autonomous systems

Autonomous systems are rapidly becoming an integrated part of the modern life. Safe and secure navigation and control of these systems present significant challenges in the presence of uncertainties, physical failures, and cyber attacks. In this paper, we formulate a navigation and control problem for autonomous systems using a multilevel control structure, in which the high‐level reference commands are limited by a saturation function, whereas the low‐level controller tracks the reference by compensating for disturbances and uncertainties. For this purpose, we consider a class of nested, uncertain, multiple‐input–multiple‐output systems subject to reference command saturation, possibly with nonminimum phase zeros. A multirate output‐feedback adaptive controller is developed as the low‐level controller. The sampled‐data (SD) design of this controller facilitates the direct implementation on digital computers, where the input/output signals are available at discrete time instances with different sampling rates. In addition, stealthy zero‐dynamics attacks become detectable by considering a multirate SD formulation. Robust stability and performance of the overall closed‐loop system with command saturation and multirate adaptive control are analyzed. Simulation scenarios for navigation and control of a fixed‐wing drone under failures/attacks are provided to validate the theoretical findings.     

An interval observer for uncertain continuous‐time linear systems

To design robust interval observers for uncertain continuous‐time linear systems, a new set‐integration approach is proposed to compute trajectory tubes for the estimation error. Because this approach, the order‐preserving condition on the dynamics of the estimation error is no longer required. Therefore, synthesis methods can be used to compute observer gains that reduce the impact of the system uncertainties on the accuracy of the estimated state enclosures. The performance of the proposed approach is showcased through illustrative numerical examples.     

Improved Input and State Estimation for Linear Stochastic Systems with Direct Feedthrough

This paper is concerned with the problem of joint input and state estimation for linear stochastic systems with direct feedthrough. Based on the fact that each unknown input between any two time steps is always bounded, a novel improved algorithm is proposed. Compared with existing results, this algorithm can effectively enhance estimation accuracy. Moreover, the stability of the algorithm is also discussed. Finally, an illustrative example is given to demonstrate the effectiveness of the proposed approach.     

建筑产业转型升级新时代下高职建筑工程技术特色专业建设问题的新思考

随着建筑业技术进步和转型升级,高职建筑工程技术专业建设应顺应新时代要求,产教融合,办出特色。本文提出了“四个对接一个融合”的特色专业建设新思考。     

Power flow calculation for a distribution system with multi-port PETs: an improved AC-DC decoupling iterative method

Recently, power electronic transformers (PETs) have received widespread attention owing to their flexible networking, diverse operating modes, and abundant control objects. In this study, we established a steady-state model of PETs and applied it to the power flow calculation of AC–DC hybrid systems with PETs, considering the topology, power balance, loss, and control characteristics of multi-port PETs. To address new problems caused by the introduction of the PET port and control equations to the power flow calculation, this study proposes an iterative method of AC–DC mixed power flow decoupling based on step optimization, which can achieve AC–DC decoupling and effectively improve convergence. The results show that the proposed algorithm improves the iterative method and overcomes the overcorrection and initial value sensitivity problems of conventional iterative algorithms.     

Utilizing the autocatalysis of Co to prepare low-cost WC-Co powder for high-performance atmospheric plasma spraying

A novel method of incorporating fluidized bed chemical vapor deposition (FBCVD) with electroless plating was developed to effectively prepare the core-shell structured WC-Co composite powders. The Co nanoparticles decorated on the surface of WC particles by FBCVD acted as active catalysts for the subsequent electroless plating process. The particle size and quantity of the decorated Co particles determined the electroless plating rate but the particle size played more important role. For the conditions tested, the maximum electroless plating rate of 2.34 mg/g/min was obtained by using an optimal FBCVD pretreatment at 750°C for 3 minutes. WC-12Co composite powders with a commercial composition widely used for atmospheric plasma spraying (APS) were efficiently prepared. The composite powders exhibited excellent suitability for APS by forming a homogenous Co-W-C ternary liquid stream. The APS coating is not only well-bonded with the substrate but also consisted of hard nonequilibrium Co₃W₃C and W₂C phases with a uniform distribution. Both remarkably improved the hardness and tribological properties of the APS coating.     

Werkstoffliche Aufbereitung von Wärmedämmverbundsystemen

Due to increasing energy requirements for buildings, thermal insulation composite systems (TICS) have been used to insulate building facades since the 1970s. In view of the longevity of these composite materials, there has been an increased amount of TICS waste in recent years. Since there is no current recycling concept for these systems, an enormous resource efficiency potential remains unused. Due to the complexity of composite materials this study focuses on the pretreatment and discusses different processing steps in detail.