Tallinn University of Technology

About: Tallinn University of Technology is a education organization based out in Tallinn, Estonia. It is known for research contribution in the topics: European union & Oil shale. The organization has 3688 authors who have published 10313 publications receiving 145058 citations. The organization is also known as: Tallinn Technical University & Tallinna Tehnikaülikool.

Wide Input Voltage Range Photovoltaic Microconverter With Reconfigurable Buck–Boost Switching Stage

Abstract: This paper presents a novel soft-switching galvanically isolated buck-boost dc–dc converter as a module-integrated converter for photovoltaic (PV) applications. It features three major operating modes: boost, normal, and buck mode. Their proper distribution over the input voltage range enables wide voltage regulation capabilities, i.e., close to those of nonisolated power optimizers. The proposed control algorithm requires only one buck-boost switching stage that performs voltage regulation by means of the switching stage reconfiguration with smooth transition between the modes. The design guidelines and the digital control system for PV applications are provided. The module-integrated converter was verified experimentally with a solar array simulator. The converter showed good maximum power point tracking performance and a peak efficiency of nearly 97%.

Guyer-Krumhansl-type heat conduction at room temperature

Abstract: Results of heat pulse experiments in various artificial and natural materials are reported in this paper. The experiments are performed at room temperature with macroscopic samples. It is shown that temperature evolution does not follow Fourier's law but is well explained by the Guyer-Krumhansl equation. The observations confirm the ability of non-equilibrium thermodynamics to formulate universal constitutive relations for thermomechanical processes.

Current practice in identifying and treating cardiovascular risk, with a focus on residual risk associated with atherogenic dyslipidaemia

Abstract: A panel of European experts on lipids and cardiovascular disease discussed clinical approaches to managing cardiovascular risk in clinical practice, including residual cardiovascular risk associated with lipid abnormalities, such as atherogenic dyslipidaemia (AD). A simplified definition of AD was proposed to enhance understanding of this condition, its prevalence, and its impact on cardiovascular risk. Atherogenic dyslipidaemia can be defined by high fasting triglyceride levels (≥2.3 mmol/L) and low high-density lipoprotein cholesterol (HDL-c) levels (≤1.0 and ≤1.3 mmol/L in men and women, respectively) in statin-treated patients at high cardiovascular risk. The use of a single marker for the diagnosis and treatment of AD, such as non-HDL-c, was advocated. Interventions including lifestyle optimization and low-density lipoprotein (LDL)-lowering therapy with statins (±ezetimibe) are implemented by all experts. Treatment of residual AD can be performed with the addition of fenofibrate, since it can improve the complete lipoprotein profile and reduce the risk of cardiovascular events in patients with AD. Specific clinical scenarios in which fenofibrate may be prescribed are discussed, and include patients with very high triglycerides (≥5.6 mmol/L), patients who are intolerant or resistant to statins, and patients with AD and at high cardiovascular risk. The fenofibrate–statin combination was considered by the experts to benefit from a favourable benefit–risk profile. Cardiovascular experts adopt a multifaceted approach to the prevention of atherosclerotic cardiovascular disease, with lifestyle optimization, LDL-lowering therapy, and treatment of AD with fenofibrate routinely used to help reduce a patient's overall cardiovascular risk.

Scattering of the fundamental torsional mode at an axial crack in a pipe.

Abstract: A quantitative study of the interaction of the T(0,1) torsional mode with an axial defect in a pipe is presented. The results are obtained from finite element simulations and experiments. The influence of the crack axial extent, depth, excitation frequency, and pipe circumference on the scattering is examined. It is found that the reflection from a defect consists of a series of the wave pulses with gradually decaying amplitudes. Such behavior is caused by the shear waves diffracting from the crack and then repeatedly interacting with the crack due to circumferential propagation. Time-domain reflection coefficient analysis demonstrates that the trend of the reflection strength for different crack lengths, pipe diameters, and frequencies from a through-thickness crack satisfies a simple normalization. The results show that the reflection coefficient initially increases with the crack length at all frequencies but finally reaches an oscillating regime. Also, at a given frequency and crack length the reflect...