Adaptive Backstepping Control for Fractional-Order Nonlinear Systems with External Disturbance and Uncertain Parameters Using Smooth Control

In this paper, we consider controlling a class of single-input-single-output (SISO) commensurate fractional-order nonlinear systems with parametric uncertainty and external disturbance. Based on backstepping approach, an adaptive controller is proposed with adaptive laws that are used to estimate the unknown system parameters and the bound of unknown disturbance. Instead of using discontinuous functions such as the $\mathrm{sign}$ function, an auxiliary function is employed to obtain a smooth control input that is still able to achieve perfect tracking in the presence of bounded disturbances. Indeed, global boundedness of all closed-loop signals and asymptotic perfect tracking of fractional-order system output to a given reference trajectory are proved by using fractional directed Lyapunov method. To verify the effectiveness of the proposed control method, simulation examples are presented.Comment: Accepted by the IEEE Transactions on Systems, Man and Cybernetics: Systems with Minor Revision

Modeling spacing factor requirements and measuring water permeability in hydrated Portland cement paste

Small, well-dispersed air voids in hydrated cement paste can improve workability, reduce bleeding and segregation, and improve resistance to freezing and thawing. To characterize the air void system in cement paste, not only the amount and size of air voids are important, but their distribution (spacing factor) is also significant. This thesis investigates the frost action mechanism in cement paste and how the spacing factor closely relates with it. Also, this thesis provides detailed information about testing the cement paste\u27s water permeability by using a falling head permeameter on saturated samples. Paper one is a sensitivity study from an existing modeling system for determination of maximum spacing factors. Conclusions are drawn by analyzing the existing mathematic model and comparing the theoretic values with experimental values. Paper two describes work conducted in the development of a method to test water permeability of saturated hydrated cement paste. This is a cost effective method to test the water permeability, since the work is achieved by revising of existing Ballim oxygen test. From test results and observations, several apparatus\u27 revisions have been completed. Some recommendations are provided for further improvement of the test apparatus

On Suprememum of a set in A Dedikind Complete Topological Space

The supremum for a set in a multi-dimensional, Dedikind complete topological space is defined. The example is given to illustrate that the condition of Dedilind complete is necessary for the existence of supremum

Traveling wave-based protection scheme for inverter-dominated microgrid using mathematical morphology

Inverter-dominated microgrids impose significant challenges on the distribution network, as inverters are well known for their limited contribution to fault current, undermining the performance of traditional overcurrent protection schemes. This paper introduces a new protection scheme based on the initial current traveling wave utilizing an improved mathematical morphology (MM) technology, with simplified polarity detection and new logics introduced for meshed networks and feeders with single-end measurement. The proposed protection scheme provides ultrafast response and can be adapted to varied system operational modes, topologies, fault conditions, and load conditions. Only low-bandwidth communication is required to achieve high-speed operation and adequate discrimination level in meshed networks. Simulation in PSCAD/EMTDC verifies both the sensitivity and stability of the proposed protection scheme under different microgrid operational scenarios

International White Book on DER Protection : Review and Testing Procedures

This white book provides an insight into the issues surrounding the impact of increasing levels of DER on the generator and network protection and the resulting necessary improvements in protection testing practices. Particular focus is placed on ever increasing inverter-interfaced DER installations and the challenges of utility network integration. This white book should also serve as a starting point for specifying DER protection testing requirements and procedures. A comprehensive review of international DER protection practices, standards and recommendations is presented. This is accompanied by the identifi cation of the main performance challenges related to these protection schemes under varied network operational conditions and the nature of DER generator and interface technologies. Emphasis is placed on the importance of dynamic testing that can only be delivered through laboratory-based platforms such as real-time simulators, integrated substation automation infrastructure and fl exible, inverter-equipped testing microgrids. To this end, the combination of fl exible network operation and new DER technologies underlines the importance of utilising the laboratory testing facilities available within the DERlab Network of Excellence. This not only informs the shaping of new protection testing and network integration practices by end users but also enables the process of de-risking new DER protection technologies. In order to support the issues discussed in the white paper, a comparative case study between UK and German DER protection and scheme testing practices is presented. This also highlights the level of complexity associated with standardisation and approval mechanisms adopted by different countries

Heat Dissipation Performance of Micro-channel Heat Sink with Various Protrusion Designs

This research will focus on studying the effect of aperture size and shape of the micro-channel heat sink on heat dissipation performance for chip cooling. The micro-channel heat sink is considered to be a porous medium with fluid subject inter-facial convection. Derivation based on energy equation gives a set of governing partial differential equations describing the heat transfer through the micro-channels. Numerical simulation, including steady-state thermal analysis based on CFD software, is used to create a finite element solver to tackle the derived partial differential equations with properly defined boundary conditions related to temperature. After simulating three types of heat sinks with various protrusion designs including micro-channels fins, curly micro-channels fins, and Micro-pin fins, the result shows that the heat sink with the maximum contact area per unit volume will have the best heat dissipation performance, we will interpret the result by using the volume averaging theorem on the porous medium model of the heat sink

Early Autism Diagnosis based on Path Signature and Siamese Unsupervised Feature Compressor

Autism Spectrum Disorder (ASD) has been emerging as a growing public health threat. Early diagnosis of ASD is crucial for timely, effective intervention and treatment. However, conventional diagnosis methods based on communications and behavioral patterns are unreliable for children younger than 2 years of age. Given evidences of neurodevelopmental abnormalities in ASD infants, we resort to a novel deep learning-based method to extract key features from the inherently scarce, class-imbalanced, and heterogeneous structural MR images for early autism diagnosis. Specifically, we propose a Siamese verification framework to extend the scarce data, and an unsupervised compressor to alleviate data imbalance by extracting key features. We also proposed weight constraints to cope with sample heterogeneity by giving different samples different voting weights during validation, and we used Path Signature to unravel meaningful developmental features from the two-time point data longitudinally. Extensive experiments have shown that our method performed well under practical scenarios, transcending existing machine learning methods