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Qualitative study of a well-stirred isothermal reaction model
Barbara Arcet, Maša Dukarić, Zhibek Kadyrsizova, 2020, original scientific article

Abstract: We consider a two-dimensional system which is a mathematical model for a temporal evolution of a well-stirred isothermal reaction system. We give sufficient conditions for the existence of purely imaginary eigenvalues of the Jacobian matrix of the system at its fixed points. Moreover, we show that the system admits a supercritical Hopf bifurcation.
Keywords: limit cycle, Hopf bifurcation, stability, reaction kinetics
Published in DKUM: 16.10.2023; Views: 162; Downloads: 8
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The impact of macroprudential policy on credit growth in nine euro area economies
Eva Lorenčič, Robert Volčjak, Mejra Festić, 2023, original scientific article

Abstract: In this paper, we investigate the impact of macroprudential policy measures (bundled together into a macroprudential policy index, MPI) on the nonfinancial corporate sector credit and household credit growth using a one-step system GMM empirical research method. The goal of our paper is to test whether contractionary macroprudential policy stymies credit growth rate and whether expansionary macroprudential policy spurs credit growth rate in selected Euro Area economies (Austria, Belgium, Finland, Germany, Ireland, Italy, Netherlands, Slovenia, and Spain) over the period 2008Q4–2018Q4. We test two hypotheses: H1: The tightening of macroprudential policy measures reduces the non-financial corporate sector credit growth rate, and H2: The tightening of macroprudential policy measures reduces the growth rate of household credit. Based on our empirical results, we can confirm the first hypothesis. In contrast, the second hypothesis can be neither confirmed nor rejected since the explanatory variable of interest (MPI) is statistically insignificant in the second model.
Keywords: macroprudential policy, systemic risk, financial stability, dynamic panel data, one-step system GMM
Published in DKUM: 05.09.2023; Views: 145; Downloads: 4
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Implementation of climate change effects on slope stability analysis
Tamara Bračko, Bojan Žlender, Primož Jelušič, 2022, original scientific article

Abstract: The objective of this study is to determine the impacts of expected climate change on slope stability. For this purpose, the case study of a slope instability, that was triggered in 2021 was selected. The stability analysis was performed considering the theory of rainfall infiltration and using Geo-Studio’s SEEP/W module for the surface infiltration model of the slope. A parametric stability analysis of the slope was conducted to determine the importance of climate change on slope stability. Conditions for changes in volumetric water content, water permeability, porewater pressure, and groundwater flow are important. When soil permeability is low, the factor of safety decreases during rainfall events and on the days following, while when permeability is higher, safety increases after rainfall events. The effect of lower cohesion is nearly linear, with the factor of safety decreasing by 0.1 for every 1 kPa less cohesion. The increase in net infiltration of water may be the most critical factor for slope instability. The results of the analysis indicate that timely reduction of water net infiltration through planting and proper surface water runoff from the upper road and slope would be a relatively simple and inexpensive measure compared to the cost of remediating the landslide, considering expected climate change. Therefore, it is advisable to analyze all slopes with respect to the expected climate change, taking into account the potential impacts of climate change.
Keywords: climate change adaptation, slope stability, rainfall infiltration, water net infiltration, seepage analyses
Published in DKUM: 18.08.2023; Views: 315; Downloads: 26
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The dynamics of a duopoly Stackelberg game with marginal costs among heterogeneous players
Atefeh Ahmadi, Sourav Roy, Mahtab Mehrabbeik, Dibakar Ghosh, Sajad Jafari, Matjaž Perc, 2023, original scientific article

Abstract: One of the famous economic models in game theory is the duopoly Stackelberg model, in which a leader and a follower firm manufacture a single product in the market. Their goal is to obtain the maximum profit while competing with each other. The desired dynamics for a firm in a market is the convergence to its Nash equilibrium, but the dynamics of real-world markets are not always steady and can result in unpredictable market changes that exhibit chaotic behaviors. On the other hand, to approach reality more, the two firms in the market can be considered heterogeneous. The leader firm is bounded rationale, and the follower firm is adaptable. Modifying the cost function that affects the firms' profit by adding the marginal cost term is another step toward reality. We propose a Stackelberg model with heterogeneous players and marginal costs, which exhibits chaotic behavior. This model's equilibrium points, including the Nash equilibrium, are calculated by the backward induction method, and their stability analyses are obtained. The influence of changing each model parameter on the consequent dynamics is investigated through one-dimensional and two-dimensional bifurcation diagrams, Lyapunov exponents spectra, and Kaplan-Yorke dimension. Eventually, using a combination of state feedback and parameter adjustment methods, the chaotic solutions of the model are successfully tamed, and the model converges to its Nash equilibrium.
Keywords: nonlinear dynamics, game theory, stability analysis, public goods
Published in DKUM: 02.08.2023; Views: 262; Downloads: 20
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Simon Hudales, 2022, master's thesis

Abstract: For the design of slender structures consisting of plates and tubes, such as supporting structures at cranes, buckling is beside stress and fatigue often the governing failure criteria. Stability analysis of such structures is usually performed using the GMNIA method according to DIN EN 1993. For this purpose, a suitable geometric equivalent imperfection must be applied to the structure. Buckling inherent shapes are determined for this purpose and scaled according to applicable safety concepts. Including imperfections in stability analysis can generally be relevant for the load-bearing behavior of a structure. Within this master thesis work, the influence of the initial geometric imperfection on stability behaviour is investigated. This study examines the influence, that imperfections imposed on members subjected to tensile stress have on stability behaviour. Tensile members of structures are identified and initial geometric imperfection is imposed on them in addition to critical members, that are subjected to compression stress. It is shown, that including imperfections on tensile members in stability analysis, has only a minor influence on stability behaviour and stiffness of the structure, both reducing it just slightly. Further on, investigation on boom model, that is supporting structure of the crawler crane, is made. Boom model consist of main chord members and diagonals connecting them. At the joint connection of boom and two diagonal members, one subjected to tension and one subjected to compression stress, appears area of high shear stresses. Influence of the direction, that imperfection is imposed on the diagonal member, and what is the influence on the stability behaviour and structural strength is presented in this work. Most severe case of the two chosen direction is pointed out and discussed.
Keywords: stability analysis, initial geometric imperfections, thin-walled structures, finite element method
Published in DKUM: 06.07.2022; Views: 431; Downloads: 49
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The Impact of Macroprudential Policy Instruments on Financial Stability
Eva Lorenčič, 2021, doctoral dissertation

Abstract: This doctoral dissertation represents a comprehensive treatment of the many facets of macroprudential policy. We start by delving into the notions of macroprudential policy, systemic risk and financial stability, describe the macroprudential policy transmission mechanism, systemic financial crises and contagion channels, as well as the Modigliani-Miller theorem and its violations. We proceed by illustrating a multitude of available macroprudential policy instruments, attempt to clarify whether capital controls can be considered a macroprudential policy instrument, describe the use and calibration of macroprudential policy instruments, and elaborate on the changes to the EU macroprudential policy framework after the enactment of the Capital Requirements Regulation II and Capital Requirements Directive V. Next, we describe interactions between macroprudential policy and other policies, in particular microprudential, monetary, fiscal and structural policies. We attempt to answer the question of whether macroprudential policy should be entrusted to a central bank, a financial supervisory authority, or the government. Furthermore, we investigate whether countries should reciprocate each other’s macroprudential policy stance. Moreover, we review the existing research regarding the impact of macroprudential policy instruments on financial stability. We attempt to answer the question of whether the existence of a macroprudential policy framework could have prevented the Global Financial Crisis of 2007. Last but not least, we conduct our own empirical assessment of the impact of macroprudential policy instruments on financial stability in six euro area countries (Belgium, Cyprus, Germany, Spain, Ireland and Netherlands) over sixteen quarters (from 2015 Q1 (inclusive) to 2018 Q4 (inclusive)) by using the quantitative research method of panel econometrics. We tested three hypotheses: H1: Macroprudential policy instruments (common equity tier 1 ratio; loans to deposits ratio; non-deposit funding as percentage of total funding; leverage ratio; interconnectedness ratio; and coverage ratio for non-performing exposures) enhance financial stability, as measured by credit growth. H2: Macroprudential policy instruments (common equity tier 1 ratio; loans to deposits ratio; non-deposit funding as percentage of total funding; leverage ratio; interconnectedness ratio; and coverage ratio for non-performing exposures) enhance financial stability, as measured by house price growth. H3: Macroprudential policy instruments (common equity tier 1 ratio; loans to deposits ratio; non-deposit funding as percentage of total funding; leverage ratio; interconnectedness ratio; and coverage ratio for non-performing exposures) reduce cyclical fluctuations of the economy, as measured by the amplitude of the deviations of the actual economic growth rate from its long-run trend, thereby contributing to financial stability. Our empirical results suggest that, of the investigated macroprudential policy instruments, common equity tier one ratio, coverage ratio, and interconnectedness ratio exhibit the predicted impact on credit growth rate and on the deviation of the actual economic growth rate from its long-run trend. Furthermore, common equity tier one ratio, loans to deposits ratio, and leverage ratio exhibit the predicted impact on house price growth rate. The non-deposit funding ratio does not exhibit the expected impact on any of the response variables. Hence, we can only partly confirm hypotheses 1, 2 and 3. Our conclusions are in line with contemporary research on macroprudential policy. Taking into account the existing empirical research, combined with our findings as presented in this dissertation, a case can be made for the usage of carefully crafted macroprudential policy instruments which target selected financial and macroeconomic variables with the ultimate goal of attaining financial stability of the financial system as a whole.
Keywords: Macroprudential policy, macroprudential instruments, systemic risk, financial stability
Published in DKUM: 03.05.2022; Views: 711; Downloads: 71
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A practical method for the optimal design of continuous footing using ant-colony optimization
Boonchai Ukritchon, Suraparb Keawsawasvong, 2016, original scientific article

Abstract: The objective of this paper is to present a practical method for the optimal design of a continuous footing subjected to vertical and horizontal loads. The design problem of finding the optimal size of footing as well as the minimum steel reinforcement is formulated in a nonlinear minimization form. The continuous footing is subjected to the vertical and horizontal loads acting on the top of the column. There are four design variables in the design problem, i.e., the width of the footing, the thickness of the footing, the soil-embedment depth, and the amount of steel reinforcement. The required geotechnical constraints include the bearing capacity, overturning, as well as global sliding and local sliding at the footing corners. Short-term stability and long-term stability are considered simultaneously in the same formulation. The structural constraints are enforced to control the shear force and bending moment within the section resistance. The formulation of the problem’s constraints leads to the nonlinear programming, whose objective function is to minimize the total cost of the footing material, including the concrete and steel reinforcement. The optimal solution is solved using the ant-colony optimization algorithm MIDACO. The proposed optimization method is demonstrated through the actual design of the footing for supporting a large machine moving on rails.
Keywords: optimal design, footing, stability, nonlinear programming, ant-colony optimization
Published in DKUM: 18.06.2018; Views: 1267; Downloads: 76
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A stability assessment of coastal cliffs using digital imagery
Igor Ružić, Čedomir Benac, Ivan Marović, Suzana Ilić, 2015, original scientific article

Abstract: The investigated area around the Stara Baška settlement (the island of Krk, NE channel part of the Adriatic Sea) is in a delicate geodynamic balance. Marine erosion is quite prominent and the recorded cliff retreat between 1966 and 2004 was from 4 to 5 metres. The cliff slopes are formed in talus breccias. Strong waves and formations of wave-cut notches are the main causes of the cliff’s instability. The secondary causes are the weathering and erosion of the soil and rocks on the cliff. The slump of the cliff slope can occur in a rock mass with higher strength parameters, where the notches are cut a few metres inward into the toe of the cliff slope. A combined method for the stability analysis of the coastal cliffs was tested; this incorporates the cantilever-beam model and the structure-from-motion (SfM) photogrammetry. This method can provide highly detailed 3D geometrical data of the cliff, which can then be used in the calculations of the stability model. This is particularly important in a stability analysis of lithologically heterogeneous rocks such as breccias with varied geometry, which cannot be easily replaced by a rectangular surface. The simple and useful SfM method overcomes the limitations of traditional surveys in estimating the cliff overhang surface and the notch length.
Keywords: marine erosion, cliff stability, SfM photogrammetry, Krk island, Adriatic sea
Published in DKUM: 15.06.2018; Views: 1378; Downloads: 156
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Lessons learnt from field tests in some potentially unstable slopes in Switzerland
Sarah Springman, Armin Askarinejad, Francesca Casini, Sven Friedel, Peter Kinzler, Philipp Teysseire, Andrea Thielen, 2012, original scientific article

Abstract: Rain-induced slope instability is a significant natural hazard in Switzerland, Slovenia and elsewhere in Europe. This contribution was prepared especially for the 12th Šuklje Symposium, and recognises that landslides occur both in mountain regions as well as in lowland regions during and following extreme-rainfall conditions. The Institute (and Professorship) for Geotechnical Engineering at the Swiss Federal Institute of Technology (ETH Zürich) has been engaged over several years in projects concerned with the characterisation, monitoring and modelling behaviour of slopes in mainly granular porous media across the full range of altitudes in Switzerland. A link is made to the doyen of the Šuklje day and then three case histories are presented and discussed to demonstrate the principal reactions to seasonal rainfall. A small slip was released in two of these cases and the “triggering” factors have been investigated and are discussed in this contribution. It transpires that the mode of inslope drainage influences the way in which the ground saturates and hence the volume of the potentially unstable ground. Simple stability analyses using limit equilibrium and soil parameters that have been amended to account for unsaturated soil behaviour were found to function well for slopes in largely granular media.
Keywords: rain-induced landslides, slope stability, case histories, monitoring, characterisation, modelling
Published in DKUM: 13.06.2018; Views: 1069; Downloads: 131
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Non-linear finite-element modelling of room and pillar mine workings including the strain-softening behaviour of the rock mass
Salim Bensehamdi, Abdelbaki Seriani, 2008, original scientific article

Abstract: A two-dimensional model adopting post-failure criteria was used to simulate the behaviour of the rock mass and the development of yield zones around room and pillar mine workings. The model conformed to the strain-softening behaviour of the rock mass and accounted for its post-failure residual strength. The structural-stability-analysis approach accounted for the main features of the mine structures’ yield produced during loading through changes in the rock material’s stiffness and the subsequent evolution of the stresses. A comprehensive parametric analysis was performed and the inevitable effect of the interaction of the roof, pillar and floor on the overall stability limit of the mine was investigated. The numerical results clearly showed that the finite-element linear models could not realistically represent the true behaviour of the mine structure. However, they clearly demonstrated the limitations of the finite-element linear solutions in representing the true behaviour of the mine structure, particularly when the rock-mass structure is relatively weak, and that a non-linear approach was justified.
Keywords: non-linear FE analysis, yielding, plastic zones, room and pillar mining, residual strength, stability assessment
Published in DKUM: 05.06.2018; Views: 1030; Downloads: 140
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