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This study investigates the thermal buckling in railway infrastructures, which can cause derailments and safety risks. The research analyses the influence of various parameters on thermal buckling, focusing on misalignment and ballast resistance. Using a finite element model, curved and tangent tracks are simulated, considering rail sections, sleeper materials, fastener stiffness and initial imperfections. Results demonstrate that ballast resistance is the most critical factor, with compacted ballast increasing buckling temperatures by up to 127%. Additionally, rail imperfections significantly impact temperature increases. A new design guide is proposed for operating conditions under different conditions. [ABSTRACT FROM AUTHOR]

Summary: This article studies the problem of indirect adaptive state feedback control for a heterogeneous MIMO network with input and matched uncertainties. A mechanical network composed of two‐wheeled robots is proposed to validate the developed methodology. Within the network, a reference system is defined, and each robot has wireless communication between them. Likewise, for control design, specific adaptive laws are adopted through matching conditions to approximate the dynamics of each agent, which are partially unknown and constructed. The inclusion of an optimal adaptive modification is considered for the suppression of input uncertainties. This methodology, along with the distributed adaptive control and identification, is validated with Lyapunov‐based stability analysis. The presented control scheme guarantees that all closed‐loop signals are bounded and ensures that synchronization errors converge asymptotically to zero. Finally, simulations oriented to the application problem mentioned are presented to validate the effectiveness of the control scheme. [ABSTRACT FROM AUTHOR]

A major concern of the power quality in distributed systems is related to the mitigation of voltage imbalances. This function can be implemented directly in the control system of the distributed generation power converters working simultaneously with the standard operation modes. This study presents a negative-sequence voltage elimination technique for distributed generators in grid-feeding operation mode. The proposal guarantees a complete elimination of the negative-sequence voltage, while operating without a priori in-depth knowledge of the grid configuration and its characteristics. The proposed control architecture is presented together with its pseudocode, a controller flowchart and a discussion of the implementation aspects. A closed-loop modelling is derived based on a complex transfer function approach, which is used to determine stability margins and control design guidelines. A laboratory setup was implemented to verify the performance of the proposed strategy. [ABSTRACT FROM AUTHOR]

A distributed population games algorithm is proposed to solve the dispatch problem in microgrids to respond dynamically to the requirements of the system. This study extends the distributed replicator dynamics (RD) algorithm, it has four main contributions. First, the authors apply the distributed RD to a distributed generator dispatch over a communication topology in a microgrid test system. Second, they consider power losses of the networked microgrid on the distributed RD. Third, they propose an algorithm to estimate robust loss coefficients of the network considering different demand patterns through a combination of two heuristic optimisation algorithms. Finally, the uncertainties of wind power are considered as a renewable generation integration case. The simulation results show that the proposed distributed control algorithm of a microgrid is able to integrate the economic dispatch problem with frequency control considering the entire network topology. [ABSTRACT FROM AUTHOR]

SUMMARY Optimal control problems for switched nonlinear systems are investigated. We propose an alternative approach for solving the optimal control problem for a nonlinear switched system based on the theory of moments. The essence of this method is the transformation of a nonlinear, nonconvex optimal control problem, that is, the switched system, into an equivalent optimal control problem with linear and convex structure, which allows us to obtain an equivalent convex formulation more appropriate to be solved by high-performance numerical computing. Consequently, we propose to convexify the control variables by means of the method of moments obtaining semidefinite programs. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Metabolic syndrome is a cluster of metabolic and cardiovascular symptoms: insulin resistance (IR), obesity, dyslipemia. Hypertension and vascular disorders are central to this syndrome. After a brief historical review, we discuss the role of sympathetic tone. Subsequently, we examine the link between endothelial dysfunction and IR. NO is involved in the insulin-elicited capillary vasodilatation. The insulin-signaling pathways causing NO release are different to the classical. There is a vasodilatory pathway with activation of NO synthase through Akt, and a vasoconstrictor pathway that involves the release of endothelin-1 via MAPK. IR is associated with an imbalance between both pathways in favour of the vasoconstrictor one. We also consider the link between hypertension and IR: the insulin hypothesis of hypertension. Next we discuss the importance of perivascular adipose tissue and the role of adipokines that possess vasoactive properties. Finally, animal models used in the study of vascular function of metabolic syndrome are reviewed. In particular, the Zucker fatty rat and the spontaneously hypertensive obese rat (SHROB).This one suffers macro- and microvascular malfunction due to a failure in the NO system and an abnormally high release of vasoconstrictor prostaglandins, all this alleviated with glitazones used for metabolic syndrome therapy. [ABSTRACT FROM AUTHOR]