Conservation managers regularly burn vegetation to regenerate habitat for fire-dependent species. When determining the time since fire at which to burn, managers model change in a species’ occurrence ...over time, post-fire (fire-response curve) and identify the time since fire associated with decline in occurrence. However, where species exhibit variability in their fire response across space, using a single fire-response curve to determine the timing of burns may lead to burning habitat at an inappropriate time since fire. We tested if elevation, local topography, soil properties, vegetation type or evapotranspiration affect the fire response of the endangered Mallee Emu-wren Stipiturus mallee and its hummock-grass habitat Triodia scariosa in southeastern Australia (n = 217). Previous work on the Mallee Emu-wren found a unimodal fire response with decline in occurrence at ~30–50 yr since fire and a time window of occurrence of ~30 yr. We found that time since fire and elevation interact to affect the Mallee Emu-wren fire response. At high elevations (55–98 m), Mallee Emu-wrens declined in occurrence at ~50 yr since fire, with a time window of occurrence of 20–40 yr. However, at low elevations (28–55 m), Mallee Emu-wrens showed no decline in occurrence with increasing time since fire with a time window of occurrence of up to 107 yr. Extent cover of Tall T. scariosa showed similar patterns to the Mallee Emu-wren, indicating that vegetation structure is a likely driver of variability in the Mallee Emu-wren fire response. We speculate that the effect of low elevation is mediated by increased soil nutrient and water availability for key plants. We used our findings to map the appropriate time since fire at which to burn to regenerate habitat for the Mallee Emu-wren across the study region. We recommend no burning for regeneration across one-third of potential habitat, because the Mallee Emu-wren showed no decline in occurrence in these areas. We recommend managers model variability in species’ fire responses across space to improve the timing of burns for regeneration.
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BFBNIB, FZAB, GIS, IJS, INZLJ, KILJ, NLZOH, NMLJ, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK, ZRSKP
We assess the effects of recent ECB’s unconventional monetary policy (UMP) measures by estimating a global VAR that exploits panel variation amongst all euro area economies and explicitly takes into ...account cross-country interdependencies. Most euro area members benefit from these measures but with substantial heterogeneity, whose extent has been evolving over time and peaked with the sovereign debt crisis. Cross-country spillovers account for a sizable fraction of such dispersion, and substantially amplify effects. Countries with more fragile banking systems benefit the least from unconventional monetary policy measures, and especially so in terms of output gains. Importantly, this heterogeneity implies that the effects on real activity of the whole currency union get substantially dampened. In this respect, we also document that UMP shocks imply significantly smaller and less persistent effects than those arising from conventional interest rate surprises.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
We review the extensive literature on systemic risk and connect it to the current regulatory debate. While we take stock of the achievements of this rapidly growing field, we identify a gap between ...two main approaches. The first one studies different sources of systemic risk in isolation, uses confidential data, and inspires targeted but complex regulatory tools. The second approach uses market data to produce global measures which are not directly connected to any particular theory, but could support a more efficient regulation. Bridging this gap will require encompassing theoretical models and improved data disclosure.
In this paper, we develop a new non-ordinary state-based peridynamic method to solve transient dynamic solid mechanics problems. This new peridynamic method has advantages over the previously ...developed bond-based and ordinary state-based peridynamic methods in that its bonds are not restricted to central forces, nor is it restricted to a Poisson’s ratio of 1/4 as with the bond-based method. First, we obtain non-local nodal deformation gradients that are used to define nodal strain tensors. The deformation gradient tensors are used with the nodal strain tensors to obtain rate of deformation tensors in the deformed configuration. The polar decomposition of the deformation gradient tensors are then used to obtain the nodal rotation tensors which are used to rotate the rate of deformation tensors and previous Cauchy stress tensors into an unrotated configuration. These are then used with conventional Cauchy stress constitutive models in the unrotated state where the unrotated Cauchy stress rate is objective. We then obtain the unrotated Cauchy nodal stress tensors and rotate them back into the deformed configuration where they are used to define the forces in the nodal connecting bonds. As a first example we quasi-statically stretch a bar, hold it, and then rotate it ninety degrees to illustrate the methods finite rotation capabilities. Next, we verify our new method by comparing small strain results from a bar fixed at one end and subjected to an initial velocity gradient with results obtained from the corresponding one-dimensional small strain analytical solution. As a last example, we show the fracture capabilities of the method using both a notched and un-notched bar.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•Fragmentation was present at the height of the European sovereign debt crisis.•ECB's intervention in 2012 partially restored interconnectedness across member states.•Core countries remain ideal ...candidates for an optimal currency area, adding fuel to the financial fragility hypothesis.•Further integration is necessary to alleviate convergence inconsistencies across EMU member states.
This study employs dynamic connectedness as a measure of financial risk synchronization considering government bond yields in 11 EMU member states. In particular, large values of the relevant index can be an indication of comparable levels of risk further implying that the common currency area consists of a financially sensible set of countries. By contrast, small connectedness values can be an indication of fragmentation whereupon certain countries are considered to be safer than others. The latter would be detrimental for the EMU as it fuels financial fragility, which practically stipulates that crises occur as a result of self-fulfilling market fears. The results are based on a daily dataset which spans between 1st September 2003 and 31st August 2018. Findings show that fragmentation was present at the height of the European sovereign debt crisis and that the interconnectedness has not yet reverted to its pre-2009 levels. In addition, core countries appear to transmit shocks to periphery countries although, occasionally, there are noteworthy disparities. Further investigating these disparities on a pairwise connectedness level – which helps to identify sensible pairs of countries in terms of financial risk – shows that core countries dominate this exercise, with the exception of the bilateral relation between Italy and Spain. The fact that most periphery countries of our sample are not included in these pairs raises concerns and calls for a more substantial integration.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•An efficient and accurate vehicle-track-subgrade spatial coupled dynamics model is constructed.•Combined with the fixed interface modal synthesis method and wheel/rail contact theory, the joint ...simulation of ABAQUS and UM is realized.•Take the average value of 10 groups of irregularities for track irregularity.•System dynamic characteristics of the 400 km/h and 350 km/h vehicle speeds under subgrade differential settlement conditions are compared.•The increase of train speed has a great impact on the vertical acceleration of rail.
Whether the existing ballastless track subgrade settlement control standard of 350 km/h is applicable to the high-speed train of 400 km/h remains to be further research. This paper established a complete rigid flexible coupling dynamic model of vehicle-track-subgrade space based on the finite element method and multi-body dynamics theory. Combined with the fixed interface modal synthesis method and wheel/rail contact theory, the joint simulation of ABAQUS and UM is realized. The dynamic response of 400 km/h high-speed train under the condition of subgrade differential settlement is analyzed and compared with the current 350 km/h high-speed train. The results show that under the same subgrade differential settlement condition, when the train speed increases from 350 km/h to 400 km/h, the wheel rail interaction increases significantly, but does not exceed the specification limit. The amplitude of derailment coefficient is far lower than the maximum specification limit, while the amplitude of wheel load reduction rate exceeds the quasi-static limit in the specification. The impact of the increase of train speed on the lateral stability of the vehicle is greater than that on the vertical stability of the vehicle. At 400 km/h, each stability index of the train does not exceed the maximum specification limit, and sufficient safety margin is reserved. The increase of train speed has a great impact on the vertical acceleration of rail, and has little impact on the vertical acceleration of track plate and baseplate. In summary, the current subgrade settlement control standard of 350 km/h high-speed railway is also applicable to 400 km/h high-speed trains, and there is room for further speed increase.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Objective In response to stability alarm faults occurring in CR200J EMU trailer and control cars in certain sections, it is necessary to analyze the factors affecting the dynamics performance to ...analyze the causes and address the issues. Method Tracked measurements are conducted on the wheel wear status of a set of CR200J EMU trailer and control cars. The actual rail profiles along the operating routes of vehicles are measured to identify the development patterns of wheel wear. Through SIMPACK software simulation, and combined with real wheel-rail matching conditions, the impact of wheel wear on vehicle dynamics performance is analyzed. Result & Conclusion The wheel wear of CR200J EMU trailer and control cars mainly concentrates at the rolling circle. As wheel wear increases, changes occur in the wheel-rail contact relationship, leading to a linear increase in wheel equivalent conicity, and noticeable changes in lateral stability indicators of the vehicles. Some sections of the measured track profiles exhibit
•The design of central bank interventions can exacerbate the bank-sovereign nexus.•This paper studies the ECB’s 2011 Long-Term Refinancing Operation.•Long-term ECB lending induced banks to purchase ...shorter-term collateral securities.•This collateral trade expanded demand for (shorter-term) peripheral sovereign debt.•Ex-post, the collateral trade recapitalized banks and reduced public funding costs.
The design of lender-of-last-resort interventions can exacerbate the bank-sovereign nexus. During sovereign crises, central bank provision of long-term liquidity incentivizes banks to purchase high-yield eligible collateral securities matching the maturity of the central bank loans. Using unique security-level data, we find that the European Central Bank’s 3-year Long-Term Refinancing Operation caused Portuguese banks to purchase short-term domestic government bonds, equivalent to 10.6% of amounts outstanding, and pledge them to obtain central bank liquidity. The steepening of eurozone peripheral sovereign yield curves right after the policy announcement is consistent with the equilibrium effects of this “collateral trade.”
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•A non-linear piecewise state function is designed to describe maintenance states.•A high-level maintenance planning model for high-speed trains is formulated.•The original model is linearized using ...a big M method.•Develop a simulated annealing algorithm to solve the relaxation model.•Conduct a real-world case study with 124 trains from the China Shanghai Railroad.
For safety reasons, a high-speed train needs to carry out the preventive maintenance when its accumulated running mileage or time reaches a predefined threshold. This paper formulates the train high-level preventive maintenance planning problem as a 0-1 programming model. A novel state function is designed to describe whether a train is under maintenance or not. By using this function, the constraint for restricting the total number of trains under maintenance can be formulated reasonably well. A linearization technique is also employed to refine the original non-linear state function into a linear one. To handle large-scale instances, a simulated annealing algorithm is proposed for solving the problem and is applied to a real-world case study from Shanghai Railway Bureau (SRB), a regional railway operator under China Railway. The optimized results yield a total cost of 3,619,200 standard train-km in terms of remaining mileage. In addition, sensitivity analyses based on the real-world case study reveal some interesting insights. We have delivered the results to SRB as a useful and efficient decision support tool for their high-level maintenance planning work.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•We estimate the effect of ECB and Federal Reserve quantitative easing (QE) on the dollar-euro exchange rate at horizons relevant for policymakers.•We derive a theoretically-consistent local ...projection regression from the standard asset pricing formulation of exchange rate determination.•We use future changes in central banks' balance sheets relative size to proxy for unobserved QE shocks and instrument them with QE announcements.•A typical ECB or Federal Reserve expansionary QE shock in our sample raised the relative balance sheet by 20% and depreciated the exchange rate by 7%.•Currency depreciation reflectslower short-term rate differentialsand adjustments in deviations from covered and uncovered interest parity.•Changes in expectations about the future monetary policy stance, reflecting a “signalling” channel, also add to the QE impact on exchange rates.
We estimate the effects of quantitative easing (QE) measures by the ECB and the Federal Reserve on the US dollar-euro exchange rate at frequencies and horizons relevant for policymakers. To do so, we derive a theoretically-consistent local projection regression equation from the standard asset pricing formulation of exchange rate determination. We then proxy unobserved QE shocks by future changes in the relative size of central banks’ balance sheets, which we instrument with QE announcements in two-stage least squares regressions in order to account for their endogeneity. We find that QE measures have large and persistent effects on the exchange rate: The typical ECB or Federal Reserve expansionary QE announcement in our sample resulted in an increase in the relative balance sheet of about 20% and, in turn, in a persistent exchange rate depreciation of around 7%. Regarding transmission channels, we find that a relative QE shock that expands the ECB’s balance sheet relative to that of the Federal Reserve depreciates the euro against the US dollar by reducing euro-dollar short-term money market rate differentials, by widening the cross-currency basis and by eliciting adjustments in “residual” deviations from interest parity. Changes in the expectations about the future monetary policy stance, reflecting the “signalling” channel of QE, also contribute to the exchange rate response to QE shocks.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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