基于整车刚-柔耦合多体动力学模型的车架动态应力分析

以60 t交流电传动铰接式自卸车车架为研究对象,根据拓扑原理作出整车的结构拓扑图。在此基础上,先建立整车多刚体系统动力学模型,然后建立考虑车架弹性变形的铰接车刚-柔耦合多体动力学模型,并对其进行仿真分析。提取车架关键位置的动态应力-时间历程曲线,验证设计的安全性,并为下一步铰接式自卸车的设计改进和车架的疲劳寿命预测分析提供重要参考依据。     

Competing management approaches in large engineering projects: The Dutch RandstadRail project

The management of large engineering projects is often a combination of the focus on planning and control, and the ambition to be flexible given the complexity and uncertainties that characterises these kinds of projects. However, control and flexibility impose contradictory requirements upon the management of these projects. The literature on project management reflects this contradiction. Some authors underline that projects require firm planning and control, thus downplaying the role of flexibility. Others emphasise that projects require flexibility and responsiveness, thus moving away from rigid planning and control. In this contribution, we suggest that in practice project managers acknowledge the weakness of both extremes and therefore strive to combine the two. Moreover, we argue that project success is at risk when project managers do not succeed in meeting the requirements of control and flexibility. To be able to investigate how these competing requirements are dealt with in practice, a framework is developed. The usefulness of the framework is explored by applying the framework to the large engineering project Randstadrail—a light rail project in The Netherlands.     

上海东方体育中心

在上海东方体育中心落成之时,回顾体育中心的设计过程和构思要义,在承袭GMP一贯严谨、理性、简洁的原则基础上,展现灵活、开放、明亮、变化的性格,凸显其独特性。文章就总体设计、单体设计、新技术运用、质量控制等方面详细阐述了项目的设计概念、设计手法、成功和遗憾。     

Significance of polymer matrix on the resistive switching performance of lead-free double perovskite nanocomposite based flexible memory device

Polymer based resistive switching (RS) is one of the most rapidly growing memory technology that is being developed for next-generation flexible/wearable devices. In this work, we have chosen two types of host polymer matrix to support the Pb-free Cs₂AgBiBr₆ double perovskite nanofillers. Selection of poly(methyl methacrylate) (PMMA) and polyethylene oxide (PEO) is based on their nature of insulating and ionic conductivity respectively. To eliminate the dominance of electrode on (RS), Au and ITO were chosen as top and bottom electrode respectively. The PEO based device with or without nanofiller did not show significant differences in device performance. On the contrary, substantial impact of nanofiller in PMMA based devices could be observed. Interestingly, with the concentration of 2% Cs₂AgBiBr₆ nanofillers in both the polymer matrix, the devices exhibited adequate bipolar memory switching behavior. However, the PMMA composite device (with 2% nanofiller) exhibited excellent RS properties such as low operating voltage, high current ON/OFF ratio, long endurance and retention in both normal and bending mode. Low value of ON/OFF ratio in PEO composite device could be attributed to higher conductivity of PEO polymer matrix that result into high current in the OFF state. Finally, the indispensable results in the PMMA nanocomposite based flexible device was hypothesized by using energy band diagram on the basis of charge trapping/de-trapping inside the functional matrix and pave the way for the development of next-generation flexible electronics.     

Separation Units 4.0 – Trennapparate heute und morgen

The chemical industry will face serious challenges in the coming decade: compliance with climate protection targets, impacts from the “Energiewende”, and the increasing importance of circular economy affect the entire value chain. To maintain the competitiveness of this central industrial sector, innovative approaches are required, from the process level to the apparatus level and down to the scale of individual phenomena. This article presents current developments and future fields of action for separation units that can make valuable contributions to the named challenges.     

同步带传动机械手的建模与振动控制研究

为了实现硅片在测试过程中的自动传输,设计了一种同步带传动的机械手.由于同步带的柔性,在运动的过程中不可避免的带来振动.为了得到平稳的运动,建立了同步带传动机械手的数学模型,从机械设计和控制算法两方面来抑制机械手的振动,并通过计算机仿真进行了验证.     

基于非侵入式负荷监测的居民侧灵活性资源评估方法

居民用户具备巨大的灵活性潜力,充分挖掘并合理利用居民侧灵活性资源有助于提升电网的灵活性。本文利用低频功率数据和深度学习模型,提出了一种基于非侵入式负荷监测的居民侧灵活性资源评估方法。首先,采用功率波动-跳变事件检测算法,实现对电器用电事件的定位和功率数据获取。其次,将时域卷积网络(Time Convolutional Networks,TCN)和门控循环单元(Gated Recurrent Unit,GRU)相结合,借助TCN的数据特征提取能力和GRU的非线性拟合能力,构建TCN-BiGRU负荷识别算法,以有效区分不同电器的用电负荷。然后,利用负荷识别结果对用户总功率信号进行分解,建立设备状态矩阵、设备概率矩阵和设备习惯使用区间矩阵,获取各个电器的用电信息,分析用户用能行为,得到居民侧灵活性资源评估详细结果。最后,通过实际居民用户数据验证了所提出方法的实际有效性。基于本方法所得的灵活性资源评估结果可为居民需求侧响应提供辅助决策。     

Flexible and thermally stable SiC fiber mats derived from electrospun boron-doped polyaluminocarbosilane precursors

Polymer-derived SiC fibers are critical structural and functional materials for high-temperature applications, whose service performance can be further improved by introduction of certain heterogeneous elements. Herein, flexible and thermal stable SiC fiber mats were prepared from boron-doped polyaluminocarbosilane (PACS) precursor by electro-spinning, curing and pyrolysis. Two boron-containing compounds o-carborane (oCB) and phenylboronic acid (PBA) were used as the boron sources and their effects on the properties and structure of the SiC fiber mats were investigated. The introduced oCB and PBA had obviously improved the ceramic yield of the cured fiber mats and the flexibility of the SiC fiber mats. However, PBA introduced more boron, but also more oxygen, which leaded to formation of more amorphous SiC_xO_y phases. Although only a small amount of boron was introduced by oCB, a more significant improvement in the thermal stability of the SiC fiber mat was obtained. This work provided a practical approach for fabrication of flexible and thermally stable SiC fiber mats.     

Success of local flexibility market implementation: A review of current projects

The development of distributed energy sources will challenge the management of the electrical system. Local flexibility markets (LFMs) are a promising solution to coordinate the dispatch of distributed energy sources. The LFM development is in its infancy, and numerous challenges should be addressed. This study focuses on four topics for LFM success: the governance model, coordination issues, inc-dec gaming, and competition. Based on a review of current projects, we identify challenges related to the four topics and discuss solutions to overcome these challenges. The proposed solutions are crucial to achieving market efficiency and cannot be considered independently.     

Immobilizing imidazolium ionic liquid in flexible proton exchange membranes to modify microstructure fracture

The imidazolium ionic liquid of (Kevlar/bmimCl/SEBS)₅ membrane was immobilized in flexible proton exchange membranes (PEMs) with the spin coating technology. In the prepared (Kevlar/bmimCl/SEBS)₅ membrane, the imidazolium ionic liquid of 1-butyl-3-methylimidazolium chloride (bmimCl) functioned as glue to modify the microstructure fracture from the stretching operation through occupying the cracks. The proton conduction resistance was reduced with the well-ordered distribution of components in the multilayered microstructure. Although the doped phosphoric acid (PA) molecules charged the proton conductivity, the imidazolium cations of bmim⁺ could participate in the proton conduction through the formation of continuous proton conduction channels. In this research, the folding and stretching operations exerted the negligible effect on microstructure and property of the prepared PEMs. Besides the modification of bmimCl, the deformation of polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SBES) molecular chains and Kevlar nanofibers in the stretching operation contributed to maintain the stable microstructure. The stretching and folding operations led to slight variation on the membrane property. Specifically, the proton conductivities were respectively 3.21 × 10^?2 S/cm and 4.16 × 10^?2 S/cm at 160 °C, which were even superior to 2.77 × 10^?2 S/cm of the pristine membranes. Furthermore, the tensile stress values of the folding and stretching membranes can reach (18.9 ± 1.19) MPa and (32.6 ± 2.63) MPa.