Spreading of disturbances in realistic models of transmission grids in dependence on topology, inertia and heterogeneity

The energy transition towards more renewable energy resources (RER) profoundly affects the frequency dynamics and stability of electrical power networks. Here, we investigate systematically the effect of reduced grid inertia, due to an increase in the magnitude of RER, its heterogeneous distribution and the grid topology on the propagation of disturbances in realistic power grid models. These studies are conducted with the DigSILENT PowerFactory software. By changing the power generation at one central bus in each grid at a specific time, we record the resulting frequency transients at all buses. Plotting the time of arrival (ToA) of the disturbance at each bus versus the distance from the disturbance, we analyse its propagation throughout the grid. While the ToAs are found to be distributed, we confirm a tendency that the ToA increases with geodesic distance linearly. Thereby, we can measure an average velocity of propagation by fitting the data with a ballistic equation. This velocity is found to decay with increasing inertia. Characterising each grid by its meshedness coefficient, we find that the distribution of the ToAs depends in more meshed grids less strongly on the grid inertia. In order to take into account the inhomogeneous distribution of inertia, we introduce an effective distance $$r_{\mathrm{eff}}$$ r eff , which is weighted with a factor which strongly depends on local inertia. We find that this effective distance is more strongly correlated with the ToAs, for all grids. This is confirmed quantitatively by obtaining a larger Pearson correlation coefficient between ToA and $$r_{\mathrm{eff}}$$ r eff than with r. Remarkably, a ballistic equation for the ToA with a velocity, as derived from the swing equation, provides a strict lower bound for all effective distances $$r_{\mathrm{eff}}$$ r eff in all power grids. thereby yielding a reliable estimate for the smallest time a disturbance needs to propagate that distance as function of system parameters, in particular inertia. We thereby conclude that in the analysis of contingencies of power grids it may be advisable that system designers and operators use the effective distance $$r_{\mathrm{eff}}$$ r eff , taking into account inhomogeneous distribution of inertia as introduced in Eq. (12), to locate a disturbance. Moreover, our results provide evidence for the importance of the network topology as quantified by the meshedness coefficient $$\beta$$ β .

Influence of parameters inhomogeneity on the existence of chimera states in a ring of nonlocally coupled maps

The aim of the research is to study the influence of inhomogeneity in a control parameter of all partial elements in a ring of nonlocally coupled chaotic maps on the possibility of observing chimera states in the system and to compare the changes in regions of chimera realization using different methods of introducing the inhomogeneity. Methods. In this paper, snapshots of the system dynamics are constructed for various values of the parameters, as well as spatial distributions of cross-correlation coefficient values, which enable us to determine the regime observed in the system for these parameters. To improve the accuracy of the obtained results, the numerical studies are carried out for fifty different realizations of initial conditions of the ring elements. Results. It is shown that a fixed inhomogeneous distribution of the control parameters with increasing noise intensity leads to an increase in the range of the coupling strength where chimera states are observed. With this, the boundary lying in the region of strong coupling changes more significantly as compared with the case of weak coupling strength. The opposite effect is provided when the control parameters are permanently affected by noise. In this case increasing the noise intensity leads to a decrease in the interval of existence of chimera states. Additionally, the nature of the random variable distribution (normal or uniform one) does not strongly influence the observed changes in the ring dynamics. The regions of existence of chimera states are constructed in the plane of «coupling strength – noise intensity» parameters. Conclusion. We have studied how the region of existence of chimeras changes when the coupling strength between the ring elements is varied and when different characteristics of the inhomogeneous distribution of the control parameters are used. It has been shown that in order to increase the region of observing chimera states, the control parameters of the elements must be distributed inhomogeneously over the entire ensemble. To reduce this region, a constant noise effect on the control parameters should be used.

The model of degradation of an InGaN/GaN LED during current tests taking into account the inhomogeneous distribution of the defects density in the heterostructure

A model of the optical power degradation of an InGaN/GaN LED during testing under direct current, which takes into account the inhomogeneous distribution of the defects density in the heterostructure, is presented. According to the simulation results, the rate of degradation of the LED optical power significantly depends on the degree of inhomogeneity of the defects density distribution profile. Experimental testing of the model has been carried out. The proposed model makes it possible to predict the rate of degradation of InGaN-based LEDs with varying degrees of inhomogeneity of the defects density distribution profile and can be used to develop a technique for rejecting defective and potentially unreliable LEDs.

Karakterisasi Sifat Fisis dan Mikrostruktur Papan Gipsum dengan Variasi Komposisi Lateks

Gypsum board is one of the advanced products of gypsum material with a mixture of fiber/fiber or other materials. Gypsum board has a weakness in its physical properties that easily absorb water. Therefore, there is a need for innovation in the manufacture of gypsum boards that will produce even better quality. The manufacture of gypsum board can utilize waste materials such as coconut shells and rice husks and latex as adhesives. The mixture of gypsum board materials including: gypsum, coconut shell, and rice husk used was 70%, 15%, 15% with latex variation 10%, 12%, 14%, 16%, 18% with FAS 0.5 and drying for 28 days. The parameters of the physical properties test include: density and thickness expansion, as well as microstructural testing to determine the morphology of the gypsum board sample. Analysis of the physical properties of gypsum board obtained optimal results, namely in sample A with a variation of 10% latex composition, the density value was 1.35 g/cm3, and the thickness expansion was 5.03% which met the SNI Standard 01-4449-2006. While the microstructure produces morphological images that show inhomogeneous distribution, particle agglomeration forms, and impurities

Spreading of Disturbances in Realistic Models of Transmission Grids: Dependence on Topology, Inertia and Heterogeneity

The energy transition towards more renewable energy resources (RER) profoundly affects the frequency dynamics and stability of electrical power networks. Here, we investigate systematically the effect of reduced grid inertia, due to an increase in the magnitude of RER, its heterogeneous distribution and the grid topology on the propagation of disturbances in realistic power grid models. These studies are conducted with the DigSILENT PowerFactory software. By changing the power generation at one central bus in each grid at a specific time, we record the resulting frequency transients at all buses. Plotting the time of arrival (ToA) of the disturbance at each bus versus the distance from the disturbance, we analyse its propagation throughout the grid. While the ToAs are found to be distributed, we confirm a tendency that the ToA increases with geodesic distance linearly. Thereby, we can measure an average velocity of propagation by fitting the data with a ballistic equation. This velocity is found to decay with increasing inertia. Characterising each grid by its meshedness coefficient, we find that the distribution of the ToAs depends in more meshed grids less strongly on the grid inertia. In order to take into account the inhomogeneous distribution of inertia, we introduce an effective distance reff, which is weighted with a factor which strongly depends on local inertia. We find that this effective distance is more strongly correlated with the ToAs, for all grids. This is confirmed quantitatively by obtaining a larger Pearson correlation coefficient between ToA and reff than with r. Remarkably, a ballistic equation for the ToA with a velocity, as derived from the swing equation, provides a strict lower bound for all effective distances reff in all power grids. thereby yielding a reliable estimate for the smallest time a disturbance needs to propagate that distance as function of system parameters, in particular inertia. We thereby conclude that in the analysis of contingencies of power grids it may be advisable that system designers and operators use the effective distance reff, taking into account inhomogeneous distribution of inertia as introduced in Eq. (11), to locate a disturbance. Moreover, our results provide evidence for the importance of the network topology as quantified by the meshedness coefficient β.

Methods of subsurface microwave tomography with application of sensors based on pieces of twin-wire line.

In this paper, methods of near-field microwave tomography of the subsurface structure of dielectric inhomogeneities are proposed and studied based on the use of resonance probes with pieces of twin-wire lines as sensors. In frameworks of the quasi-static approximation, the integral equation of the inverse problem that relates measured variations of the complex capacity of the resonance system of probes placed above a medium with the inhomogeneous distribution of the complex permittivity. Based on this equation, methods and algorithms of tomography and holography have been proposed and worked out that used data of 2D scanning with variable offset between the sensor wires: (a) with the fixed direction of wires of sensor; (b) in two orthogonally related directions of sensor wires; (c) with the sensor of crossed twin-wire lines. Results of the numerical simulation demonstrate the efficiency of developed algorithms of subsurface tomography and holography.

System for detection of the inhomogeneous distribution of magnetic field based on liquid crystals with magnetic nanoparticle

The main objective of this article is to develop the basic technological principles of production of the magnetosensitive layer based on nematic liquid crystals with magnetic nanoparticles as the main component of the system, which allows obtaining a two-dimensional picture of the inhomogeneous distribution of low-frequency magnetic field and to identify the object creating this field. In work are described physical methods which allow to increase sensitivity and to expand a working frequency range of the magneto-sensitive layer based on such liquid crystals. By us it has been shown, that the time of reorientation of director in oriented liquid crystals with magnetic nanoparticles is less than the analogous reorientation time in nonoriented crystals. In work also it is shown, that to significantly increase the speed of reorientation in a magnetic field of the director of liquid crystals with magnetic nanoparticles is possible if submitting an additional magnetic field with given amplitude. This method allows to increase sensitivity to a magnetic field and to receive parametrical amplification of signals in liquid crystals with magnetic nanoparticles. In the conclusion on the basis of liquid crystals with magnetic nanoparticles the scheme of system of detection of inhomogeneous magnetic field is described.

Inhomogeneous distribution of lithic clasts within the Daskop granophyre dike, Vredefort impact structure: Implications for emplacement of impact melt in large impact structures

ABSTRACT The Vredefort granophyre dikes have long been recognized as being derived from the now-eroded Vredefort melt sheet. One dike, in particular, the Daskop granophyre dike, is notable for a high abundance of lithic clasts derived from various stratigraphic levels. In this study, we mapped the distribution of the clasts throughout the continuously exposed section of the dike using field mapping and aerial drone photography and attempted to constrain the emplacement mechanisms of the dike. We found that the clasts are not homogeneously spread but instead are distributed between clast-rich zones, which have up to 50% by area clasts, and clast-poor zones, which have 0–10% by area clasts. We examined three models to explain this distribution: gravitational settling of clasts, thermally driven local assimilation of clasts, and mechanical sorting of clasts due to turbulent flow. Of the three models, the gravitational settling cannot be supported based on our field and geophysical data. The assimilation of clasts and turbulent flow of clasts, however, can both potentially result in inhomogeneous clast distribution. Zones of fully assimilated clasts and nonassimilated clasts can occur from spatial temperature differences of 100 °C. Mechanical sorting driven by a turbulent flow can also generate zones of inhomogeneous clast distribution. Both local assimilation and mechanical sorting due to turbulent flow likely contributed to the observed distribution of clasts.