Now showing 1 - 2 of 2
  • Publication
    Electric Load Probability Density Estimation using Root-Transformed Local Linear Regression
    (2023)
    Elhouty, Begad B.
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    El-Fouly, Tarek H. M.
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    Zahawi, Bashar
    Probability density estimation of stochastic electric load is of importance nowadays in power system operations and urban planning due to the uncertainties in network demand that affects the operating states of power systems. This in turn requires accurate and reliable methods to estimate network loads, especially in distribution networks. This paper proposes employing the root-unroot method in combination with local linear regression for estimating electric load probability density. Using measured load data obtained for a range of commercial enterprises, the performance of the proposed model is compared with two kernel density estimation models and two traditional parametric models (Gaussian and Gamma) and is assessed using a variety of error metrics and statistical tests. Results confirm the accuracy of the nonparametric models over the parametric models with the root transform model performing the best across all error metrics and K-S goodness-of-fit test.
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  • Publication
    Heart Rate Variability Analysis Reveals a Non-monotonic Relationship between Humanin Concentration and Cardiac Autonomic Regulation
    (2022) ;
    Yousef, Hibba
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    Khandoker, Ahsan H.
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    Tarvainen, Mika P.
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    Jelinek, Herbert F.
    Oxidative stress (OS) has been shown to have a negative effect on the autonomic nervous system (ANS) and on ANS modulation of heart rate. Mitochondrial ATP production is the main source of reactive oxygen species (ROS) and hence the regulation of ROS becomes an important issue in maintaining optimal ANS functionality. Humanin (HN), a mitochondrial-derived peptide, plays an important role in lowering OS. Sympathovagal balance was assessed in 124 healthy participants through heart rate variability (HRV) analysis and compared across changes in HN concentrations divided into quintiles, with values of HN ranging from 64.6 to 343.2 pg/mL. Significant differences included various frequency domain and nonlinear HRV parameters, particularly between first and fourth HN quintiles with p values < 0.001 for recurrence plot analysis (RPA), detrended fluctuation analysis (DFA) a1 and Poincaré plot ratio SD1/SD2. The results revealed non-monotonic relationships between measures of HRV and HN concentration. A mitohormetic type of relationship was observed with HRV features increasing and then decreasing with increasing HN concentration. These results are consistent with previous findings of the importance of HN levels in regulating OS and extend these by revealing a concomitant effect on the modulation of cardiac rhythm by the ANS.
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