Comprehensive Robust Analysis for Controller Tuning in Principal Component Active Control Systems

This work comprehensively studies principal component active control systems, where plant uncertainty and input constraints are included for the stability analysis. Theoretical tools such as the time-lifting method, the Small Gain theorem and the Integral Quadratic Constraints theorem are exploited intensively in the thesis. We present two sets of results: decoupled robust criteria and improved robust criteria. The former ones are obtained under significant simplified assumptions, but clearly define the stability regions of the controller parameters. They can be used in the preliminary controller tuning to facilitate such process. The latter robust criteria complement the previous ones in the sense that they are more accurate than the existing ones by including several practical considerations in the analysis. For this reason, they stand for the main contribution of this work. Developed from these conditions, a controller design guidance is suggested and validated on two rotor vibration reduction applications, EC-145 and H-34 helicopter rotor model. It is observed that by using the robust results and following the design technique provided in this work, the controller can achieve very good level of performance with robustness guaranteed. The principal component control strategy is further benchmarked against the H∞ methods, which highlights the strengths and weaknesses of each approach. Last but not least, we also explore the use of multi-tonal control approach on the EC-145 rotor model. It is shown that all the analyses in the thesis can be easily extended to such control method, which makes this work more appealing.</div

Mandatory environmental reporting in Australia: An in-depth analysis of quantity and quality

The study addresses the ongoing debate on the effectiveness of mandatory environmental reporting regulation in the Australian context. We conduct a longitudinal in-depth quantitative and qualitative analysis to evaluate the mandatory environmental reporting practice by Australian listed companies in terms of the changes in companies’ compliance with s.299(1)(f), and changes in reporting quantity and quality over 21 years (from 1997 to 2017 inclusive). We measure the disclosure quality from a multidimensional and innovative perspective: the comprehensiveness, negativity and the substance of the disclosure. Adopting the institutional perspective of legitimacy theory and the various dynamics of the legitimacy framework developed by Suchman (1995), as well as a substantive legitimation perspective, we extend the interpretive power of legitimacy theory in the area of mandatory environmental reporting. The results show that, overall, the mandatory environmental reporting in Australia is improving with respect to increased compliance level to s.299(1)(f), increased quantity and quality. Our research provides an in-depth examination of the process by which mandatory environmental reporting regulation attain influence. Our findings show that 299(1)(f) remains effective 20 years after its adoption

Setting local economic growth targets: does it mitigate nationwide policy uncertainty?

Institutional theory holds that local governance is essential in shaping regional economic activity. This study evaluates whether local economic growth targets offset the detrimental effect of nationwide policy uncertainty on local business performance. Regression analyses of data from industrial firms and manually collected data on city economic growth targets in China show that higher local growth targets result in greater corporate investment, conditional on nationwide policy uncertainty, and that the impact is substantial through financial subsidies and allocating credit resources. However, local discretion in economic growth target setting might cause investment misallocation and efficiency loss.</p

Robust Analysis for Principal Component Active Control Systems

Principal component active control is of great interest in recent times because of its extensive use in vibration and noise reduction applications. Existing analyses for such control systems mainly focus on simplified representations of the closed-loop system to obtain robust stability conditions, but they exclude key practical considerations, such as open-loop dynamics, periodic time-varying effects generated by the transformations between the time-domain harmonic signals and the estimation of their Fourier coefficients, multirate issues caused by the plant and the controller operating at different sampling rates, modeling errors, and particular ways of scaling the control actions. The contribution of this work is to include all the afore-mentioned effects to provide more accurate robustness conditions, which complement existing controller tuning procedures. The robustness analysis is conducted by first exploiting the time-lifting method to reformulate the linear-periodic-time-variant part of the discrete-time system into an equivalent linear-time-invariant representation. Then using the theoretical tool of integral quadratic constraints, standard forms of plant uncertainty and scaling of the control actions are incorporated. A vibration control example based on the Airbus EC-145 helicopter main rotor with On-Blade actuators is included to demonstrate the benefits of the contributions. The proposed design results are benchmarked against the mixed-sensitivity H∞ method, highlighting strengths, and weaknesses by each approach for this particular application

Heat-Treatment-Induced Compositional Evolution and Magnetic State Transition in Magnetic Chalcogenide Semiconductor GeFeTe without Structural Phase Change

Control of magnetic properties in diluted magnetic semiconductors (DMSs) using external stimuli is a prerequisite for many spintronic applications. Fe-doped chalcogenide semiconductors are promising candidate materials for future spintronic devices since they offer the possibility of magnetic switching by their fast and reversible transition between amorphous and crystalline phases. However, for many proposed applications, magnetic manipulation in crystalline DMSs without a structural change is highly desirable. Thus, the ability to externally control the magnetism of magnetic chalcogenide semiconductors without structural phase change is of significance to enhance their application potential. Here we find that the annealing process could induce an antiferromagnetic (AFM)–ferromagnetic (FM) transition in magnetic chalcogenide semiconductor GeFeTe epilayers without deteriorating the crystal structure. The impact of heat treatment on magnetization in Ge_1–<i>x</i>Fe_<i>x</i>Te film depends on Fe concentration. The present data indicate that the AFM–FM transition originates from the evolution of Fe phase composition. This study gives an insight into the correlation between Fe phase composition, electronic structure, and magnetism in GeFeTe thin films

Binary logistic regression analysis of factors associated with four chronic diseases.

<p>Binary logistic regression analysis of factors associated with four chronic diseases.</p

Distribution of socio-demographic characteristics and risk factors for four chronic diseases.

<p>Distribution of socio-demographic characteristics and risk factors for four chronic diseases.</p

Developing a Place–Time-Specific Transmissibility Index to Measure and Examine the Spatiotemporally Varying Transmissibility of COVID-19

The transmission rate of COVID-19 varies by location and time. A proper measure of the transmissibility of an infectious disease should be place- and time-specific, which is currently unavailable. This research aims to better understand the spatiotemporally changing transmissibility of COVID-19. It contributes to COVID-19 research in three ways. First, it presents a generally applicable modeling framework to estimate the transmissibility of COVID-19 in a specific place and time based on daily reported case data, called space-time effective reproduction number, denoted as Rst. Then, the developed model is used to create a spatiotemporal data set of Rst  values at the county level in the United States. Second, it investigates relationships between Rst  and dynamically changing context factors with multiple machine learning and spatial modeling techniques. The research examines the relationships from a cross-sectional perspective and a longitudinal perspective separately. The longitudinal view allows us to understand how local human dynamics and policy factors influence changes in Rst over time in the place, whereas the cross-sectional view sheds light on the demographic, socioeconomic, and environmental factors behind spatial variations of Rst at a specific time slice. Some general trends of the relationships are found, but the level of impact by each context factor varies geographically. Third, the best performing local longitudinal models have promising potential to simulate or forecast future transmissibility. The random forest and the exponential regression models based on time-series data gave the best performances. These models were further evaluated against ground truth data of county-level reported cases. Their good prediction accuracies in the case study prove that these machine learning models are promising in their ability to predict transmissibility in hypothetical or foreseeable scenarios.</p

sj-tif-3-pie-10.1177_09544089221123408 - Supplemental material for Experimental study of centrifugal pump as turbine with S-blade impeller

Supplemental material, sj-tif-3-pie-10.1177_09544089221123408 for Experimental study of centrifugal pump as turbine with S-blade impeller by Xiaohui Wang, Zanxiu Wu, Hao Yang, Xingjie Zhang, Junhu Yang and Senchun Miao in Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering</p

Synthesis and Catalytic Activity of Amino Acids and Metallopeptides with Catalytically Active Metallocyclic Side Chains

Two approaches to prepare amino acids with catalytically active organometallic side chains are presented. These methods are notable in that they provide access either free or N-protected compounds that are structurally analogous to naturally occurring amino acids. The N-protected organometallic amino acids are compatible with standard peptide coupling conditions and can be used to prepare catalytically active metallopeptides