Overshoot Factor Research Articles

New Zealand Fault-Rupture Depth Model v.1.0: A Provisional Estimate of the Maximum Depth of Seismic Rupture on New Zealand’s Active Faults

ABSTRACT We summarize estimates of the maximum rupture depth on New Zealand’s active faults (“New Zealand Fault-Rupture Depth Model v.1.0”), as used in the New Zealand Community Fault Model v1.0 and as a constraint for the latest revision of the New Zealand National Seismic Hazard Model (NZ NSHM 2022). Rupture depth estimates are based on a combination of two separate model approaches (using different methods and datasets). The first approach uses regional seismicity distribution from a relocated earthquake catalog to calculate the 90% seismicity cutoff depth (D90), representing the seismogenic depth limit. This is multiplied by an overshoot factor representing the dynamic propagation of rupture into the conditional stability zone, and accounting for the difference between regional seismicity depths and the frictional properties of a mature fault zone to arrive at a seismic estimate of the maximum rupture depth. The second approach uses surface heat flow and rock type to compute depths that correspond to the thermal limits of frictional instabilities on seismogenic faults. To arrive at a thermally-based maximum rupture depth, these thermal limits are also multiplied by an overshoot factor. Both the models have depth cutoffs at the Moho and/or subducting slabs. Results indicate the maximum rupture depths between 8 (Taupō volcanic zone) and >30 km (e.g., southwest North Island), strongly correlated with regional thermal gradients. The depths derived from the two methods show broad agreement for most of the North Island and some differences in the South Island. A combined model using weighting based on relative uncertainties is derived and validated using constraints from hypocenter and slip model depths from recent well-instrumented earthquakes. We discuss modifications to the maximum rupture depths estimated here that were undertaken for application within the NZ NSHM 2022. Our research demonstrates the utility of combining seismicity cutoff and thermal stability estimates to assess the down-dip dimensions of future earthquake ruptures.

Transverse wave dynamics in short tubes with axisymmetric headwall injection

This work describes both traveling and standing vorticoacoustic waves in circular tubes that are driven by axisymmetric headwall injection. In this process, perturbation tools, field decomposition, and boundary-layer theory are jointly used. First, perturbation expansions are initiated to linearize the Navier–Stokes equations. Second, a Helmholtz decomposition of the first-order disturbances is pursued to identify a suitable set of acoustic wave equations. The last step consists of solving for the vortical mode using boundary-layer theory and a viscous expansion of the unsteady rotational set. At the outset, an explicit formulation for arbitrary headwall injection is obtained and confirmed both numerically and through limiting process verifications; the latter take into account special cases involving uniform and bell-shaped injection profiles. The resulting formulation is then described using both laminar and turbulent injection patterns. Using four canonical cases, the characteristics of the evolving vorticoacoustic wave, including its penetration depth, spatial wavelength, and overshoot factor, are systematically explored and discussed. Several fundamental flow features are also unraveled including the radial, tangential, and axial velocities of the time-dependent vortical field. Most rotational flow features are found to depend on the penetration number, the Strouhal number, and the distance from the centerline. The corresponding standing modes are expressed in closed form and shown to be appreciable in view of their amplitudes that twice exceed those associated with strictly traveling waves. Finally, by extending the boundary-layer analysis from the headwall to the sidewall, a uniformly valid wave approximation is achieved, which remains observant of the no-slip requirement everywhere.

Renewability and emergy footprint at different spatial scales for innovative food systems in Europe

Food production is increasingly being challenged by limited resources of energy and land as well as by growing demand for food. In a future with less availability of fossil fuels, land area will become very important for capturing the flow-limited renewable resources. Emergy assessment has been applied to calculate scale dependent indicators, which account for the land area needed, if agricultural systems were to be supported solely on renewable sources. These indicators are designated emergy footprints (EmFs) and expand the concept of support area defined previously in emergy accounting. The EmF (in ha) is calculated based on renewable empower densities which convert resource use into area equivalents able to capture renewable flows. The spatial division between on-site, local and non-local land areas applied in this study, identifies where the support area is located in order to apply a site-specific renewable empower density. A new indicator applying the EmF is the emergy overshoot factor, which estimates the ratio between EmF and the geographical system boundary (in ha). We apply this approach on three innovative food supply systems in Europe located at farms characterised by combining high diversity, reduced use of resources, nutrient cycling and local sales. The question is whether this type of food system may be considered sustainable from a resource use point of view measured as resource use efficiency by means of unit emergy value (UEV), renewability (Ron-site and Rglobal), direct and indirect occupation of land on different spatial scales (EmF and Emergy overshoot factor) and productivity per ha of the directly observed areas and the EmF area, respectively. Labour inputs constituted between 13 and 80% of the total emergy flow. The proportion of resource use from renewable sources was between 31 and 60% when excluding the inputs of direct labour. The food system with the lowest UEV, excluding direct labour, had the highest emergy overshoot factor, which even exceeded the global average of seven. However, this system had the highest productivity. The system with the highest UEV, excluding direct labour, had the lowest overshoot factor. In conclusion, each food system strategy has its pros and cons and it depends on the priorities, which is judged the most sustainable from an emergy point of view.

Experimental Research and Simulation on VFTO Mitigation by Ferrite Rings in UHV GIS

Experiments were performed on two different ultra-high voltage gas-insulated switchgear test circuits to evaluate the mitigation performance of ferrite R2KB rings with very fast transient overvoltages (VFTOs). Significant decreases in the overshoot factor and the VFTO level were observed, although the steepness was not much improved owing to saturation. It was found that ferrite rings are more effective for VFTO mitigation at the source side than at the load side. Simulations were carried out with a new circuit model of the ferrite ring, and the simulation results were consistent with the experimental results. The method of drawing the contour plot of VFTO and very fast transient current in the time-space domain was proposed to facilitate the analysis. With this method, the principle of determining the optimal installation location of ferrite rings for the best mitigation performance was clarified.

PASSIVE VERTICALIZATION IN PATIENTS WITH SYMPTOMATIC PRECEREBRAL STENOSЕS IN ACUTE STROKE

stenoses of precerebral arteries, to determine predictors of the complications of verticalization in order to perform a more differentiated approach to the implementation of the protocol to ensure the safety of the process. Design and methods. The study included 50 patients with hemispheric ischemic stroke. Group 1 (n = 30) included patients without hemodynamically signiicant stenoses of the brachiocephalic arteries (BCA), group 2 (n = 20) included patients with hemodynamically signiicant stenoses of the BCA. Verticalization was carried out on a tilt-table «Vario-Line» («Beka») on the 1, 2, 3, 4, 5 and 14 day from the onset of the disease. Results. In group 2 an earlier decline in the rate of cerebral blood low (CBF), as well as the re-reduction rate of the CBF during the session of verticalization were detected. During the interruption between the sessions, indicators of autoregulation recovered more slowly in patients from group 2. Moreover, the cerebral autoregulation indicators were decreased during the course of verticalization, by 14 day only a quarter of these patients had a ratio of 10 % overshoot.Conclusions. Patients with hemodynamically signiicant stenoses of symptomatic BCA need to use a special regimen of verticalization that would appear «gentle» in order to prevent the complications of verticalization. Assessment of cerebral blood low autoregulation by the overshoot factor can help to identify patients with the increased risk of complications.

PASSIVE VERTICALIZATION IN PATIENTS WITH SYMPTOMATIC PRECEREBRAL STENOSЕS IN ACUTE STROKE

stenoses of precerebral arteries, to determine predictors of the complications of verticalization in order to perform a more differentiated approach to the implementation of the protocol to ensure the safety of the process. Design and methods. The study included 50 patients with hemispheric ischemic stroke. Group 1 (n = 30) included patients without hemodynamically signiicant stenoses of the brachiocephalic arteries (BCA), group 2 (n = 20) included patients with hemodynamically signiicant stenoses of the BCA. Verticalization was carried out on a tilt-table «Vario-Line» («Beka») on the 1, 2, 3, 4, 5 and 14 day from the onset of the disease. Results. In group 2 an earlier decline in the rate of cerebral blood low (CBF), as well as the re-reduction rate of the CBF during the session of verticalization were detected. During the interruption between the sessions, indicators of autoregulation recovered more slowly in patients from group 2. Moreover, the cerebral autoregulation indicators were decreased during the course of verticalization, by 14 day only a quarter of these patients had a ratio of 10 % overshoot.Conclusions. Patients with hemodynamically signiicant stenoses of symptomatic BCA need to use a special regimen of verticalization that would appear «gentle» in order to prevent the complications of verticalization. Assessment of cerebral blood low autoregulation by the overshoot factor can help to identify patients with the increased risk of complications.

Experimental Research on Suppressing VFTO in GIS by Magnetic Rings

Very-fast transient overvoltage (VFTO) is a serious threat to the insulation of extra-high voltage and ultra-high voltage power-system equipment and should be suppressed. A simpler and more reliable VFTO suppressing method than a shunt resistor is presented in this paper, which uses magnetic rings installed on the center conductor of gas-insulated switchgear (GIS). Two kinds of magnetic materials that can work under high frequency were adopted, one of which is ferrite R2KB and the other is amorphous FJ37. Measurements in a scale model with an air-insulated busbar show that ferrite R2KB rings have a better suppressing effect than amorphous FJ37 when the ring-cluster length is larger than a certain value. The ferrite R2KB rings were applied to 252-kV GIS. The test results show that ferrite R2KB rings can significantly suppress the peak value and the time to peak of VFTO. When the ring-cluster length is 40 cm and the test voltage is 140 kV of power frequency, the overshoot factor and the front steepness of VFTO can be reduced more than 50% and 20%, respectively. The test results are exiting and indicate that using magnetic rings to suppress VFTO is feasible.

Evidence for reformation of the Uranian bow shock: Hybrid simulations and comparisons with Voyager data

[1] The cyclic reformation of shock structures is still a major unresolved issue for collisionless shock physics. We investigate the Voyager 2 spacecraft's encounter with the Uranian bow shock and present the first detailed quantitative evidence that the bow shock was reforming. This evidence is based on finding very good agreement between Voyager observations of the Uranian bow shock and results from a standard 1-D hybrid simulation code run with similar plasma parameters. Specifically, the multiple large localized magnetic field enhancements B/B0 ∼ 16 observed downstream by Voyager 2, where B0 = 0.19 nT is the upstream magnetic field, are quantitatively consistent with the reforming shock found in the simulation. Moreover, the variability and large enhancement factors for B and the number density, as well as the variations of the plasma velocity, and ion temperature over an almost 2-h period including and after the shock crossing, are consistent with Voyager being very close to the reforming bow shock and with the Uranian bow shock receding planetward with the spacecraft. Additional simulations show the magnetic overshoot factor to increase approximately linearly with Alfven Mach number and to be robust against changes in magnetic field orientation (from quasi-parallel to quasi-perpendicular). These large overshoots may be important in applications involving particle acceleration and type II solar radio bursts. In addition, we estimate the effective numerical resistivity of our code by comparing simulations with varying applied resistivity. The estimated numerical resistivity found is consistent with estimates inferred from observations of Earth's bow shock by Scudder et al. (1986).

Impact ionization in semiconductors: recent progress on non‐local effects

AbstractA model of the ionization pathlength PDF is reformulated with new parameters that have more physical significance and allow further investigation. The transition from the dead space effect to the dead space plus resonance effect is investigated and a new measure, the overshoot factor, is suggested as the method for indicating the degree of resonant behaviour. The non‐local model is extended for non‐uniform electric field profiles. When this extended model is fitted to Monte Carlo data derived for four different electric field profiles, a fairly consistent set of parameters is found. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Analysis and evaluation of waveform parameters for oscillating impulse voltage

AbstractThis paper describes the effect of residual inductance of the impulse generator circuit. The analysis of waveform and the evaluation of waveform parameters were made for an oscillating lightning impulse. The peak value (overshoot factor or k‐factor), oscillation frequency, 30% value, 90% value, time to half‐value, and virtual origin are derived from the solution of third‐order derivative equation of the equivalent circuit. The comparison with the oscillating and standard lightning impulse was made. Also, the effects on overshoot, front time and the load‐side capacitance are theoretically clarified. Copyright © 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.