Dielectric screening in atomically thin boron nitride nanosheets

Two-dimensional (2D) hexagonal boron nitride (BN) nanosheets are excellent dielectric substrate for graphene, molybdenum disulfide, and many other 2D nanomaterial-based electronic and photonic devices. To optimize the performance of these 2D devices, it is essential to understand the dielectric screening properties of BN nanosheets as a function of the thickness. Here, electric force microscopy along with theoretical calculations based on both state-of-the-art first-principles calculations with van der Waals interactions under consideration, and nonlinear Thomas-Fermi theory models are used to investigate the dielectric screening in high-quality BN nanosheets of different thicknesses. It is found that atomically thin BN nanosheets are less effective in electric field screening, but the screening capability of BN shows a relatively weak dependence on the layer thickness.

Colloidal interaction between a rigid solid and a fluid drop

We present results of a theoretical study of the effect of surface deformation on a macroscopic system composed of a solid surface interacting with a fluid drop through electrostatic double-layer forces. The analysis involves numerically solving a Laplace equation suitably modified to describe the shape of a liquid drop subjected to a repulsive double-layer force. The latter is evaluated in nonlinear mean-field theory. Some analytical results are also given. The results indicate that although deformation need not be significant on the macroscopic scale, its effect on the interaction is significant and modifies the picture usually presented in DLVO theory. The decay length of the exponential repulsion deviates marginally from the Debye length, dependent on the interfacial tension of the drop. More significantly, at separations where the double-layer force becomes comparable to the internal pressure of the drop, the net force between the two bodies, the local radius of curvature of the drop, and the amount of deformation grow abruptly. The results of this work are relevant to emulsion stability, micelle, vesicle, and cell interactions, and recent experiments on bubble-particle interaction.

Michael Polanyi and Thomas Kuhn: priority and credit

The article argues that Polanyi was a likely source of influence on the theory of science that Kuhn developed in his The Structure of Scientific Revolutions (1962). The striking similarity between Kuhn’s idea of incommensurability and Polanyi’s rendering of scientific controversy in Personal Knowledge is featured here, and is used to expose a tension between Polanyi’s notions of scientific controversy and unfolding truth.

Nonlinear discrimination using support vector machine

Appropriate training data always play an important role in constructing an efficient classifier to solve the data mining classification problem. Support Vector Machine (SVM) is a comparatively new approach in constructing a model/classifier for data analysis, based on Statistical Learning Theory (SLT). SVM utilizes a transformation of the basic constrained optimization problem compared to that of a quadratic programming method, which can be solved parsimoniously through standard methods. Our research focuses on SVM to classify a number of different sizes of data sets. We found SVM to perform well in the case of discrimination compared to some other existing popular classifiers.

Reconsidering institutional cosmopolitanism : global poverty and the importance of the state in international political theory

Cosmopolitan scholarship has been at the forefront of efforts to consider political structures capable of realising justice in a more robust manner than prevailing global governance arrangements. In particular, the arguments of Thomas Pogge have contributed significantly to scholarly thinking about global poverty and his scheme of 'institutional cosmopolitanism' aspires to institutionalise human rights in the structures of global governance. This essay critiques the capacity of Pogge's cosmopolitan approach to productively guide political action in relation to global poverty by questioning whether global institutions generated by human rights are sufficient to address global poverty. The argument in this essay is that a viable guide to political action which alleviates global poverty must also take account of the potential utility of the state. This essays draws upon republican ideas to contend that cosmopolitanism needs to encompass a robust account of local institutions such as the state.

A family of simple and robust finite elements for linear and geometrically nonlinear analysis of laminated composite plates

A family of simple, displacement-based and shear-flexible triangular and quadrilateral flat plate/shell elements for linear and geometrically nonlinear analysis of thin to moderately thick laminate composite plates are introduced and summarized in this paper.

The developed elements are based on the first-order shear deformation theory (FSDT) and von-Karman’s large deflection theory, and total Lagrangian approach is employed to formulate the element for geometrically nonlinear analysis. The deflection and rotation functions of the element boundary are obtained from Timoshenko’s laminated composite beam functions, thus convergence can be ensured theoretically for very thin laminates and shear-locking problem is avoided naturally.

The flat triangular plate/shell element is of 3-node, 18-degree-of-freedom, and the plane displacement interpolation functions of the Allman’s triangular membrane element with drilling degrees of freedom are taken as the in-plane displacements of the element. The flat quadrilateral plate/shell element is of 4-node, 24-degree-of-freedom, and the linear displacement interpolation functions of a quadrilateral plane element with drilling degrees of freedom are taken as the in-plane displacements.

The developed elements are simple in formulation, free from shear-locking, and include conventional engineering degrees of freedom. Numerical examples demonstrate that the elements are convergent, not sensitive to mesh distortion, accurate and efficient for linear and geometric nonlinear analysis of thin to moderately thick laminates.

Study of 'post-critical' thought and religious epistemology : with special reference to Michael Polanyi, Paul Tillich and Thomas F. Torrance

Explores the foundational problem in epistemology posed by Immanuel Kant and illustrates, from the 'post-critical' position, with special reference to Michael Polanyi, Paul Tillich and Thomas F. Torrance, how they serve as alternative philosophical and religious responses to the Kantian critical philosophy.

Towards a southern theory of higher education

Crudely, social inclusion in Australian higher education is a numbers game. While the student recruitment departments of universities focus on ‘bums on seats’, equity advocates draw attention to ‘which bums’, in ‘what proportions’, and, more to the point, ‘which seats’, ‘where’. But if the counting of bums is crude, so is the differentiation of seats. Just distinguishing between courses and universities and scrutinizing the distribution of groups, is a limited view of equity. The most prestigious seats of learning give students access primarily to dominant forms of knowledge and ways of thinking. In terms of access, it is to a diminished higher education, for all. Further, undergraduates – particularly in their first year – are rarely credited with having much to contribute. Higher education is the poorer for it. In this paper I propose an expanded conception for social inclusion and an enlarged regard for what is being accessed by students who gain entry to university. Drawing on Connell’s conception of ‘Southern Theory’, I highlight power/knowledge relations in higher education and particularly ‘southerners’: those under‐represented in universities – often located south of ENTER (Equivalent National Tertiary Entrance Rank) cut‐offs – and whose cultural capital is similarly marginalised and discounted. While increasing regard for the importance of Indigenous knowledges is beginning to challenge the norms of higher education, we are yet to generalise such reconceptions of epistemology to include knowledges particular to people from regional and rural areas, with disabilities, and from low socioeconomic backgrounds. Nor have we really engaged with different ways of thinking about the physical and social worlds that are particular to these groups. To take account of marginalized forms of knowledge and of thinking will mean thinking differently about what higher education is and how it gets done.

Robust nonlinear distributed controller design for active and reactive power sharing in islanded microgrids

This paper presents a robust nonlinear distributed controller design for islanded operation of microgrids in order to maintain active and reactive power balance. In this paper, microgrids are considered as inverter-dominated networks integrated with renewable energy sources (RESs) and battery energy storage systems (BESSs), where solar photovoltaic generators act as RESs and plug-in hybrid electric vehicles as BESSs to supply power into the grid. The proposed controller is designed by using partial feedback linearization and the robustness of this control scheme is ensured by considering structured uncertainties within the RESs and BESSs. An approach for modeling the uncertainties through the satisfaction of matching conditions is also provided in this paper. The proposed distributed control scheme requires information from local and neighboring generators to communicate with each other and the communication among RESs, BESSs, and control centers is developed by using the concept of the graph theory. Finally, the performance of the proposed robust controller is demonstrated on a test microgrid and simulation results indicate the superiority of the proposed scheme under different operating conditions as compared to a linear-quadratic-regulator-based controller.

Global finite-time stabilisation for a class of stochastic nonlinear systems by output feedback

In this paper, the problem of global finite-time stabilisation by output feedback is considered for a class of stochastic nonlinear systems. First, based on homogeneous systems theory and the adding a power integrator technique, a homogeneous reduced order observer and control law are constructed in a recursive manner for the nominal system. Then, the homogeneous domination approach is used to deal with the nonlinearities in drift and diffusion terms; it is shown that the proposed output-feedback control law can guarantee that the closed-loop system is global finite-time stable in probability. Finally, simulation examples are carried out to demonstrate the effectiveness of the proposed control scheme.

The essential role of social theory in qualitative public health research

OBJECTIVE: To define the role of social theory and examine how research studies using qualitative methods can use social theory to generalize their results beyond the setting of the study or to other social groups. APPROACH: The assumptions underlying public health research using qualitative methods derive from a range of social theories that include conflict theory, structural functionalism, symbolic interactionism, the sociology of knowledge and feminism. Depending on the research problem, these and other social theories provide conceptual tools and models for constructing a suitable research framework, and for collecting and analysing data. In combination with the substantive health literature, the theoretical literature provides the conceptual bridge that links the conclusions of the study to other social groups and settings. CONCLUSION: While descriptive studies using qualitative research methods can generate important insights into social experience, the use of social theory in the construction and conduct of research enables researchers to extrapolate their findings to settings and groups broader than the ones in which the research was conducted.

R1SVM: a randomised nonlinear approach to large-scale anomaly detection

The problem of unsupervised anomaly detection arises in a wide variety of practical applications. While one-class support vector machines have demonstrated their effectiveness as an anomaly detection technique, their ability to model large datasets is limited due to their memory and time complexity for training. To address this issue for supervised learning of kernel machines, there has been growing interest in random projection methods as an alternative to the computationally expensive problems of kernel matrix construction and support vector optimisation. In this paper we leverage the theory of nonlinear random projections and propose the Randomised One-class SVM (R1SVM), which is an efficient and scalable anomaly detection technique that can be trained on large-scale datasets. Our empirical analysis on several real-life and synthetic datasets shows that our randomised 1SVM algorithm achieves comparable or better accuracy to deep autoen-coder and traditional kernelised approaches for anomaly detection, while being approximately 100 times faster in training and testing.

Transient stability enhancement of multimachine power systems using nonlinear observer-based excitation controller

This paper presents an approach to design a nonlinear observer-based excitation controller for multimachine power systems to enhance the transient stability. The controller is designed based on the partial feedback linearization of a nonlinear power system model which transforms the model into a reducedorder linear one with an autonomous dynamical part. Then a linear state feedback stabilizing controller is designed for the reduced-order linear power system model using optimal control theory which enhances the stability of the entire system. The states of the feedback stabilizing controller are obtained from the nonlinear observer and the performance of this observer-based controller is independent of the operating points of power systems. The performance of the proposed observer-based controller is compared to that of an exact feedback linearizing observer-based controller and a partial feedback linearizing controller without observer under different operating conditions.

Nonlinear adaptive backstepping controller design for controlling bidirectional power flow of BESSs in DC microgrids

In this paper, a nonlinear adaptive backstepping controlleris designed to control the bidirectional power flow (charging/discharging) of battery energy storage systems (BESSs) in a DCmicrogrid under different operating conditions. The controller isdesigned in such a manner that the BESSs can store the excess energyfrom the renewable energy sources (RESs) in a DC microgrid aftersatisfying the load demand and also feeding back the stored energyto the load when RESs are not sufficient. The proposed controller isalso designed to maintain a constant voltage at the DC bus, whereall components of DC microgrids are connected, while controllingthe power flow of BESSs. This paper considers solar photovoltaic(PV) systems as the RES whereas a diesel generator equipped witha rectifier is used as a backup supply to maintain the continuity ofpower supply in the case of emergency situations. The controller isdesigned recursively based on the Lyapunov control theory whereall parameters within the model of BESSs are assumed to beunknown. These unknown parameters are then estimated throughthe adaptation laws and whose stability is ensured by formulatingsuitable control Lyapunov functions (CLFs) at different stages ofthe design process. Moreover, a scheme is also presented to monitorthe state of charge (SOC) of the BESS. Finally, the performanceof the proposed controller is verified on a test DC microgrid undervarious operating conditions. The proposed controller ensures the DCbus voltage regulation within the acceptable limits under differentoperating conditions.