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Numerical determination of wind forces acting on structural elements in the shape of a curved pipe
Agnieszka Padewska-Jurczak,Piotr Szczepaniak,Zbigniew Buliński 한국풍공학회 2020 Wind and Structures, An International Journal (WAS Vol.30 No.1
This paper reports the study on development and verification of numerical models and analyzes of flow at high speed around structural elements in the shape of a curved pipe (e.g., a fragment of a water slide). Possibility of engineering estimation of wind forces acting on an object in the shape of a helix is presented, using relationships concerning toroidal and cylindrical elements. Determination of useful engineering parameters (such as aerodynamic forces, pressure distribution, and air velocity field) is presented, impossible to obtain from the existing standard EN 1991-1-4 (the so-called wind standard). For this purpose, flow at high speed around a torus and helix, arranged both near planar surface and high above it, was analyzed. Analyzes begin with the flow around a cylinder. This is the simplest object with a circular cross-section and at the same time the most studied in the literature. Based on this model, more complex models are analyzed: first in the shape of half of a torus, next in the shape of a helix.
Jiyong Woo,Belmonte, Attilio,Redolfi, Augusto,Hyunsang Hwang,Jurczak, Malgorzata,Goux, Ludovic IEEE 2016 IEEE electron device letters Vol.37 No.2
<P>In this letter, we experimentally investigate data retention in a copper (Cu)-based conductive bridge random-access memory device at a low current regime (10 mu A) in which retention is governed by factors other than just the conductive filament. Our findings show that the retention characteristics are determined by the local chemical potential of Cu between the conductive filament and its surrounding medium. Furthermore, the retention tendencies are described by the electrochemical reaction in accordance with the potential difference of Cu ions. Therefore, an appropriate quantity of Cu ions around the filament is important for achieving thermally reliable high and low resistance states over time.</P>
Lee, Hui-Young,Lee, Jae Sung,Alves, Tiago,Ladiges, Warren,Rabinovitch, Peter S.,Jurczak, Michael J.,Choi, Cheol Soo,Shulman, Gerald I.,Samuel, Varman T. American Diabetes Association 2017 Diabetes Vol. No.
<P>We explored the role of reactive oxygen species (ROS) in the pathogenesis of muscle insulin resistance. We assessed insulin action in vivo with a hyperinsulinemic-euglycemic clamp in mice expressing a mitochondrial-targeted catalase (MCAT) that were fed regular chow (RC) or a high-fat diet (HFD) or underwent an acute infusion of a lipid emulsion. RC-fed MCAT mice were similar to littermate wild-type (WT) mice. However, HFD-fed MCAT mice were protected from diet-induced insulin resistance. In contrast, an acute lipid infusion caused muscle insulin resistance in both MCAT and WT mice. ROS production was decreased in both HFD-fed and lipid-infused MCAT mice and cannot explain the divergent response in insulin action. MCAT mice had subtly increased energy expenditure and muscle fat oxidation with decreased intramuscular diacylglycerol (DAG) accumulation, protein kinase C- (PKC) activation, and impaired insulin signaling with HFD. In contrast, the insulin resistance with the acute lipid infusion was associated with increased muscle DAG content in both WT and MCAT mice. These studies suggest that altering muscle mitochondrial ROS production does not directly alter the development of lipid-induced insulin resistance. However, the altered energy balance in HFD-fed MCAT mice protected them from DAG accumulation, PKC activation, and impaired muscle insulin signaling.</P>