3,370 research outputs found

    Sources, Effects, and Modelling of Interharmonics

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    Recently, the increasing use of power electronic systems and time-variant nonlinear loads has brought number of power harmonics/interharmonics, and the power supply quality is therefore seriously threatened. The presence of interharmonics strongly poses more difficulties in modelling and measuring the distorted waveforms. Therefore, this paper reviews the sources, effects, and modelling of interharmonics. It provides a variety of crucial phenomena caused by interharmonics. More importantly, it also gives a possible solution for engineers/researchers to use appropriate tools to measure interharmonics. Some methods with implementation results are introduced and discussed for details

    Generalized Synchronization with Uncertain Parameters of Nonlinear Dynamic System via Adaptive Control

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    An adaptive control scheme is developed to study the generalized adaptive chaos synchronization with uncertain chaotic parameters behavior between two identical chaotic dynamic systems. This generalized adaptive chaos synchronization controller is designed based on Lyapunov stability theory and an analytic expression of the adaptive controller with its update laws of uncertain chaotic parameters is shown. The generalized adaptive synchronization with uncertain parameters between two identical new Lorenz-Stenflo systems is taken as three examples to show the effectiveness of the proposed method. The numerical simulations are shown to verify the results

    Nonlinear Dynamic Analysis and Synchronization of Four-Dimensional Lorenz-Stenflo System and Its Circuit Experimental Implementation

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    Recently many chaotic systems’ circuits are designed to generate phenomenon of chaos signals. The ability to synchronize chaotic circuits opens a great number of ways to use them in application signals masking. In this paper, first a new nonlinear chaotic dynamical system had be design, analyze and build circuit. Second, using GYC, partial region stability theory is applied to adaptive control for two identical chaotic systems with uncertain parameters. The results of numerical simulation are performed to verify examples of the proposed nonlinear controllers

    An Application of Nash-Moser Theorem to Smooth Solutions of One-Dimensional Compressible Euler Equation with Gravity

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    We study one-dimensional motions of polytropic gas governed by the compressible Euler equations. The problem on the half space under a constant gravity gives an equilibrium which has free boundary touching the vacuum and the linearized approximation at this equilibrium gives time periodic solutions. But it is not easy to justify the existence of long-time true solutions for which this time periodic solution is the first approximation. The situation is in contrast to the problem of free motions without gravity. The reason is that the usual iteration method for quasilinear hyperbolic problem cannot be used because of the loss of regularities which causes from the touch with the vacuum. Interestingly, the equation can be transformed to a nonlinear wave equation on a higher dimensional space, for which the space dimension, being larger than 4, is related to the adiabatic exponent of the original one-dimensional problem. We try to find a family of solutions expanded by a small parameter. Applying the Nash-Moser theory, we justify this expansion.The application of the Nash-Moser theory is necessary for the sake of conquest of the trouble with loss of regularities, and the justification of the applicability requires a very delicate analysis of the problem

    Existence and Multiplicity of Traveling Waves in a Lattice Dynamical System

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    AbstractThis work proves the existence and multiplicity results of monotonic traveling wave solutions for some lattice differential equations by using the monotone iteration method. Our results include the model of cellular neural networks (CNN). In addition to the monotonic traveling wave solutions, non-monotonic and oscillating traveling wave solutions in the delay type of CNN are also obtained

    DFT-based recursive group-harmonic energy distribution approach for power interharmonic identification

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    AbstractThe Discrete Fourier Transform (DFT) is still a widely used tool for analyzing and measuring both stationary and transient signals in power system harmonics. However, the misapplications of DFT can lead to incorrect results caused by some problems such as the aliasing effect, spectral leakage and picket-fence effect. The strategy of a DFT-based recursive Group-harmonic Energy Distribution (GED) algorithm is developed for system-wide harmonic/interharmonic evaluation in power systems. The proposed algorithm can restore individual dispersing spectral leakage energy caused by the DFT, and thus retrieve respective real harmonic/interharmonic value. Every distribution of energy minimizing iteration procedure for harmonic/interharmonic evaluation can be convergent fast, and therefore guarantee each harmonic/interharmonic magnitude and respective frequency approaches its actual value. Consequently, not only can high precision in integer harmonic measurement be retained, but also the interharmonics can be identified accurately, particularly under system frequency drift. A numerical example is presented to verify the proposed algorithm in terms of robust, fast and precise performance

    Age Effects on Spatiotemporal Dynamics of Response Inhibition: An MEG Study

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    Inhibition, the ability to suppress irrelevant information, thoughts or movements, is crucial for humans to perform context-appropriate behaviors. It was suggested that declined cognitive performance in older adults might be attributed to inhibitory deficiencies. Although previous studies have shown an age-associated reduction in inhibitory ability, the understanding regarding its cortical spatiotemporal maps remained limited. Thus, we used a whole-head magnetoencephalography (MEG) to elucidate the age effects on response inhibition, and to explore the brain activation differences in high- and low-performing seniors. We recruited 22 younger and 22 older adults to participate in the visual Go/No-go task. Both behavioral performance and neuromagnetic responses to No-go stimuli were analyzed. The behavioral results showed that the older adults made more false alarm (FA) errors than the younger adults did. The MEG results showed that the seniors exhibited declined cortical activities in middle temporal gyrus (MTG) and delayed activation in MTG, prefrontal cortex (PFC) and pre-supplementary motor area (pre-SMA). Furthermore, among the older adults, more recruitment of the left PFC was found in the high-performers than in the lower-performers. In conclusion, age-related deficiencies in response inhibition were observed in both behavioral performance and neurophysiological measurement. Our results also suggested that frontal recruitment plays a compensatory role in successful inhibition

    Caffeamide 36-13 Regulates the Antidiabetic and Hypolipidemic Signs of High-Fat-Fed Mice on Glucose Transporter 4, AMPK Phosphorylation, and Regulated Hepatic Glucose Production

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    This study was to investigate the antidiabetic and antihyperlipidemic effects of (E)-3-[3, 4-dihydroxyphenyl-1-(piperidin-1-yl)prop-2-en-1-one] (36-13) (TS), one of caffeic acid amide derivatives, on high-fat (HF-) fed mice. The C57BL/6J mice were randomly divided into the control (CON) group and the experimental group, which was firstly fed a HF diet for 8 weeks. Then, the HF group was subdivided into four groups and was given TS orally (including two doses) or rosiglitazone (Rosi) or vehicle for 4 weeks. Blood, skeletal muscle, and tissues were examined by measuring glycaemia and dyslipidemia-associated events. TS effectively prevented HF diet-induced increases in the levels of blood glucose, triglyceride, insulin, leptin, and free fatty acid (FFA) and weights of visceral fa; moreover, adipocytes in the visceral depots showed a reduction in size. TS treatment significantly increased the protein contents of glucose transporter 4 (GLUT4) in skeletal muscle; TS also significantly enhanced Akt phosphorylation in liver, whereas it reduced the expressions of phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase). Moreover, TS enhanced phosphorylation of AMP-activated protein kinase (phospho-AMPK) both in skeletal muscle and liver tissue. Therefore, it is possible that the activation of AMPK by TS resulted in enhanced glucose uptake in skeletal muscle, contrasting with diminished gluconeogenesis in liver. TS exhibits hypolipidemic effect by decreasing the expressions of fatty acid synthase (FAS). Thus, antidiabetic properties of TS occurred as a result of decreased hepatic glucose production by PEPCK and G6Pase downregulation and improved insulin sensitization. Thus, amelioration of diabetic and dyslipidemic state by TS in HF-fed mice occurred by regulation of GLUT4, G6Pase, and FAS and phosphorylation of AMPK

    Antioksidativna i citotoksična aktivnost ekstrakata mlijeka proizvedenog iz fermentirane crne soje

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    In this study, ethanol extracts from 2-day fermented black soybean milk (FBE) by immobilized Rhizopus oligosporus NTU5 have been evaluated for both antioxidant and cytotoxic activities. The results reveal that a 2-day FBE had strong 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging effect (76 %). The extracts were further fractionated by silica gel column chromatography and an unknown compound, FBE5-A, was obtained, which exhibited strong antioxidant activity. IC50 of the DPPH scavenging effect of FBE5-A was 7.5 μg/mL, which is stronger than a commonly used antioxidant, vitamin E (α-tocopherol; 17.4 μg/mL), and similar to vitamin C (ascorbic acid; 7.6 μg/mL). The cytotoxic test demonstrated that extracts of 2-day fermented broth exhibited selective cytotoxic activity towards human carcinoma cells, Hep 3B (IC50=150.2 μg/mL), and did not affect normal human lung fibroblasts, MRC-5 (p<0.05). The results indicate the potential applications of fermented black soybean milk as functional food, pharmaceutical or cancer therapy formula.U radu je ispitana antioksidativna i citotoksična aktivnost etanolnih esktrakata mlijeka dobivenog nakon 2 dana fermentacije crne soje pomoću imobiliziranoga soja Rhizopus oligosporus NTU5. Rezultati su pokazali da takvo mlijeko ima izraženu sposobnost uklanjanja slobodnih DPPH radikala (76 %). Ekstrakti su mlijeka zatim frakcionirani kromatografijom na silikagelu i izdvojen je nepoznati sastojak, nazvan FBE5-A, izraženog antioksidativnog svojstva. Sposobnost toga sastojka da uklanja slobodne DPPH radikale kudikamo je veća (IC50=7,5 μg/mL) nego vitamina E, koji se obično koristi kao antioksidans (α-tokoferol, IC50=17,4 μg/mL) i približno jednaka vitaminu C (askorbinska kiselina, IC50=7,6 μg/mL). Ispitivanje citotoksičnog učinka FBE5-A pokazalo je da selektivno djeluje na ljudske stanice raka Hep 3B (IC50=150,2 μg/mL), a pritom ne utječe na normalne fibroblaste iz pluća MRC-5 (p<0,05). Rezultati upućuju na to da se mlijeko dobiveno fermentacijom crne soje može upotrijebiti kao funkcionalna hrana i za liječenje raznih bolesti, uključujući i rak
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