Perspective of mixed matrix membranes for carbon capture

Polymeric membrane-based gas separation has found wide applications in industry, such as carbon capture, hydrogen recovery, natural gas sweetening, as well as oxygen enrichment. Commercial gas separation membranes are required to have high gas permeability and selectivity, while being cost-effective to process. Mixed matrix membranes (MMMs) have a composite structure that consists of polymers and fillers, therefore featuring the advantages of both materials. Much effort has been made to improve the gas separation performance of MMMs as well as general membrane properties, such as mechanical strength and thermal stability. This perspective describes potential use of MMMs for carbon capture applications, explores their limitations in fabrication and methods to overcome them, and addresses their performance under industry gas conditions.     

基于计算机的镀液温度智能控制系统设计

为提高镀液温度的控制精度,以计算机为平台设计了一种镀液温度智能控制系统。设计了一种模糊PID温度控制器,可实现PID控制器参数的实时在线调整。利用动态矩阵,统计过去和当前时刻的偏差,预测未来偏差,进而得到最佳输入。最后,进行了实验研究。结果表明:镀液温度智能控制系统的收敛速率快、精度高、稳定性好,能满足电镀行业的需求,具有广阔的应用前景。     

Robust predictive extended state observer for a class of nonlinear systems with time-varying input delay

ABSTRACT

This paper deals with asymptotic stabilisation of a class of nonlinear input-delayed systems via dynamic output feedback in the presence of disturbances. The proposed strategy has the structure of an observer-based control law, in which the observer estimates and predicts both the plant state and the external disturbance. A nominal delay value is assumed to be known and stability conditions in terms of linear matrix inequalities are derived for fast-varying delay uncertainties. Asymptotic stability is achieved if the disturbance or the time delay is constant. The controller design problem is also addressed and a numerical example with an unstable system is provided to illustrate the usefulness of the proposed strategy.     

Estimating epidemic coupling between populations from the time to invasion

Identifying the mechanisms by which diseases spread among populations is important for understanding and forecasting patterns of epidemics and pandemics. Estimating transmission coupling among populations is challenging because transmission events are difficult to observe in practice, and connectivity among populations is often obscured by local disease dynamics. We consider the common situation in which an epidemic is seeded in one population and later spreads to a second population. We present a method for estimating transmission coupling between the two populations, assuming they can be modelled as susceptible–infected–removed (SIR) systems. We show that the strength of coupling between the two populations can be estimated from the time taken for the disease to invade the second population. Confidence in the estimate is low if only a single invasion event has been observed, but is substantially improved if numerous independent invasion events are observed. Our analysis of this simplest, idealized scenario represents a first step toward developing and verifying methods for estimating epidemic coupling among populations in an ever-more-connected global human population.     

Fabrication of Cu/graphite film/Cu sandwich composites with ultrahigh thermal conductivity for thermal management applications

Effective thermal management of electronic integrated devices with high powder density has become a serious issue, which requires materials with high thermal conductivity (TC). In order to solve the problem of weak bonding between graphite and Cu, a novel Cu/graphite film/Cu sandwich composite (Cu/GF/Cu composite) with ultrahigh TC was fabricated by electro-deposition. The micro-riveting structure was introduced to enhance the bonding strength between graphite film and deposited Cu layers by preparing a rectangular array of micro-holes on the graphite film before electro-deposition. TC and mechanical properties of the composites with different graphite volume fractions and current densities were investigated. The results showed that the TC enhancement generated by the micro-riveting structure for Cu/GF/Cu composites at low graphite content was more effective than that at high graphite content, and the strong texture orientation of deposited Cu resulted in high TC. Under the optimizing preparing condition, the highest in-plane TC reached 824.3 W·m⁻¹·K⁻¹, while the ultimate tensile strength of this composite was about four times higher than that of the graphite film.     

Leader-following consensus of fractional-order multi-agent systems via adaptive control

This article focuses on the consensus problem of leader-following fractional-order multi-agent systems (MASs) with general linear and Lipschitz nonlinear dynamics. First, the distributed adaptive protocols for linear and nonlinear fractional-order MASs are constructed, respectively. We allow the control coupling gains to be time varying for each agent. Moreover, the adaptive modification schemes for the control gain are designed, which renders smaller control gains and thus requires smaller amplitude on the control input without sacrificing consensus convergence. Second, based on fractional-order Lyapunov stability theorem and Barbalat's lemma, two novel sufficient conditions in terms of linear matrix inequalities are provided to ensure that the leader-following consensus can be obtained in the case for any undirected connected communication graph. Furthermore, we show that the proposed algorithm also works for consensus of agents with intrinsic Lipschitz nonlinear dynamics. As a result, the proposed framework requires no global information and thus can be implemented in a fully distributed manner. Finally, the numerical simulations are given to demonstrate the effectiveness of obtained the theoretical results.     

集成式铁基质生物膜反应器自养反硝化深度脱氮

以污水厂处理水为研究对象，采用铁基质生物载体与生物膜耦合实现高效自养反硝化脱氮。考察停留时间（HRT）对系统脱氮效能的影响，通过动力学及微生物群落结构分析，揭示耦合技术的脱氮机理。结果表明：HRT为8 h，对一级A和一级B污水厂处理水，总氮(TN)平均去除率分别为95.41%和92.55%，TN处理负荷分别为0.48 kg TN/(m³·d）和0.58 kg TN/(m³·d），硝化过程氨氮(NH₄⁺-N)饱和常数分别为1.17 mg/L和0.72 mg/L，反硝化过程硝氮(NO₃^--N)饱和常数分别为0.87 mg/L和0.67 mg/L。出水水质分别达到《地表水环境质量标准》Ⅲ类、Ⅴ类水质标准。铁基质生物载体与生物膜耦合系统中微生物优势菌属为Maritimimonas、Rhodobacter和Sphaerotilus, 均为自养反硝化菌，证实了铁基质生物载体可为自养反硝化菌提供电子，实现生物自养反硝化脱氮。     

Crack initiation and propagation in braided SiC/SiC composite tubes: Effect of braiding angle

Crack initiation and propagation in three braided SiC/SiC composite tubes with different braiding angles are investigated by in situ tensile tests with synchrotron micro-computed tomography. Crack networks are precisely detected after an image subtraction procedure based on Digital Volume Correlation. FFT based simulations are performed on the full-resolution 3D images to assess elastic stress/strain fields. Quantitative measurements of the crack geometries are performed using a novel method based on grey levels. The results show that braiding angle has no obvious effect on the location of crack onsets (initiation always occurs at tow interfaces), whereas it significantly affects the paths of crack propagation. This work provides an explicit demonstration of the crack propagation scenarios with respect to the mesoscopic fibre architectures.